Methods of making fastener products

ABSTRACT

A method of forming a fastener is provided, including (a) forming, from a thermoformable material, a preform product having a sheet-form base and an array of preform stems integrally molded with and extending from the base to corresponding terminal ends; (b) heating the terminal ends of the stems to a predetermined softening temperature, while maintaining the sheet-form base and a lower portion of each stem at a temperature lower than the softening temperature; and (c) contacting the terminal ends with a contact surface that is at a predetermined forming temperature, lower than the softening temperature, to deform the terminal ends to form heads therefrom that overhang the sheet-form base. Fasteners and other methods of forming them are also provided.

This application is a divisional of U.S. Ser. No. 10/163,169, filed Jun.4, 2002 now U.S. Pat. No. 6,991,843, which is a continuation in part ofU.S. Ser. No. 09/870,063, filed May 30, 2001 now U.S. Pat. No.6,708,378, which is a divisional of U.S. Ser. No. 09/231,134, filed Jan.15, 1999, now U.S. Pat. No. 6,248,276. U.S. Ser. No. 10/163,169 is alsoa continuation in part of U.S. Ser. No. 09/808,395, filed Mar. 14, 2001now U.S. Pat. No. 7,048,818, and claims priority from U.S. ProvisionalApplication Ser. No. 60/295,937, filed Jun. 4, 2001. The entire contentsof each of the foregoing are hereby incorporated by reference.

TECHNICAL FIELD

This invention relates to touch fasteners commonly known as hook andloop fasteners and to self-engaging fasteners. In many aspects it dealswith the particular case in which hooks engage flexible loops such asare formed of fibers of thin nonwoven materials and the like.

BACKGROUND

The present invention relates to male fastener components that engage inopenings of a female component, in particular to loops formed by fibersof a nonwoven female component. The invention more particularly relatesto stem and head formations of the male elements that promote loopengageability and to methods and machines for their manufacture, andtheir use. In other aspects the invention relates to manufacture of malefastener members per se, with application for instance to so-calledself-engaging fasteners as well as to hook and loop fasteners. Theinvention in some respects, also relates to specific products of whichthe following is one example.

Attachment strips for window screens have been formed of, among otherthings, the male component of a hook and loop type fastener. To securethe screen, the male fastener elements are inserted through the openingsof the mesh material and engage the sides of the mesh openings. It isdesirable that the engagement between the male fastener elements and themesh openings provide good peel strength, so that the screen is notdetached by wind, and that the attachment strip be inexpensive andrelatively attractive.

There is a general need for male fastener components for hook and loopfasteners that provide good peel and shear strength properties indesired single or multiple directions that are relatively inexpensive tomanufacture, and a specific need for male fastener components that canfunction with low cost nonwoven loop materials.

There is also a need to be able to produce male fastener products havingdiffering functional characteristics consistently and efficiently, usingtechniques that require limited changeover in basic tooling, yet allowfor adjustments to produce the desired fastener characteristics.

Furthermore, it is especially desirable to extend the use of hook andloop fastening systems into fields of low cost products and still obtaingood fastening performance. Examples include mid- and lowest-costdisposable diapers and sanitary products, disposable packaging for lowprice products, and disposable lowest cost surgical and industrialclothing and wraps. There are many other recognized low-cost productareas to which such fasteners would be applicable.

In particular it is desirable to obtain good engagement of the malemember of the fastening system with low cost nonwoven loop products,which are characterized by their thinness and the low height to whichtheir loop-defining fibers extend.

“Good engagement” in some instances means engaging a large percentage ofhooks with low-lying loops.

“Good engagement” in other applications often requires more, as in thecase of fasteners for diapers. In such instances the hook component mustexhibit strong “peel” resistance when engaged with thin, low cost loopmaterials. With such materials, effective loop height does not permittransition of loading from the hook head to the hook stem during peelingaction, as does occur with expensive loop products that have higher loopheight. For this reason there are special problems to be addressed withhooks for thin loop structures in addition to the need to reduce thecost of the hook component.

To explain the peel considerations more fully, in a hook and loop typefastener, “peel strength” is the resistance to stripping of onecomponent from the other when a force normal to their mating surfaces isapplied to the extremity of one of the components. Such peeling force onthe component causes it to flex and progressively peel from the other.It is desirable to have such peel strength in a hook and loop fastenerthat ensures that the closure does not release under normal forces ofuse but still permits the components to be separated when required.

When the loop element is thin, as is usually the case for low-costfemale fasteners, the structure of individual loops is very short andlow-lying. In this condition, with application of a peel force, the loopexerts a force on the hook, which is essentially perpendicular to thesheet-form base and parallel to the stem of the individual hooks.Consequently the force is applied only to the heads of the hooks.

In contrast, when the loop element has a thick pile structure comprisedof long individual loops, a loop must first be pulled out to its fulllength before it can exert a significant force on a hook. As thisoccurs, the base webs to which the hooks and loops are attached areenabled to flex away from each other (see FIG. 23Y) so that at the pointof separation of hooks from such loops, the mated components are nolonger face to face. Therefore the angle at which a loop exerts itsforce on a hook is less than perpendicular. The longer the loop length,the more that angle diminishes. As a result, with a long loop component,the force not only acts on the head of the hook, but also on its stem.For very long loops, most of the resistance force is on the stem duringpeeling action.

The consequence is that for short loops, the hook head must be strongand provide much of the resistance to peel separation, while for longloops, a short rigid stem with a slight head overhang is sufficient togive high resistance to peel separation. Therefore, in many instances,in order to expand and improve the use of thin and inexpensive loopcomponents, the hook head geometry must be improved to increase strengthof engagement and produce an acceptable closure.

In many cases it is desirable to form the male hook members for use withshort loop material by molding an array of stems integrally (i.e.monolithically) with a common base, and subsequently to post-treat thestems by a pressed formation step to form loop-engageable heads. In manyinstances it is desired to use continuous processes that act in a givenmachine direction, but to find a way to do this so as to achieve a hookproduct that has good peel strength characteristics when the userapplies peel forces at a substantial angle to the machine direction, andin many cases at right angles, e.g., in the cross-machine direction.

SUMMARY OF THE INVENTION

In many aspects, the present invention employs a method of forming afastener that includes: (a) forming, from a thermoformable material, apreform product having a sheet-form base and an array of preform stemsand upper structures integrally molded with and extending from the baseto corresponding terminal ends; (b) heating the terminal ends of thestems or structure provided above the stems to a predetermined softeningtemperature, while maintaining the sheet-form base and a lower portionof each stem at a temperature lower than the softening temperature; and(c) contacting the terminal ends with a contact surface that is at apredetermined forming temperature, to reform the terminal ends to formheads therefrom that overhang the sheet-form base sufficiently to engageloops, the geometry and material of the preform structure and thecondition of reforming the terminal ends of the structure being sorelated that the formed heads are capable of peel-resistant engagementwith loops formed by fibers of thin or ultrathin nonwoven fabrics.

Preferred methods of this aspect of the invention include one or more ofthe following features. The heating is performed by a non-contact heatsource, preferably a convective heat source as by combustion products ofa flame. The polymer of the stem or structure is unoriented and ismelted into a ball-like configuration. The forming temperature issufficiently low or other conditions are provided so that thethermoformable material does not adhere to the contact surface. Water ofcombustion or steam is introduced to the contact surfaces as anon-adhering agent. The forming temperature is lower than the softeningtemperature. The contact surface comprises the cylindrical surface of aroll. The contact surface is cooled to maintain the forming temperatureduring step (c). In step (c), the heads that are formed aresubstantially disc-shaped or mushroom-shaped. The thickness of eachdisc-shaped head is from about 5 to 15% of the equivalent diameter ofthe disc, or, in the special case of convective heating of the sides ofthe terminal structure as well as the ends, as by hot combustionproducts, up to about 35% of the equivalent diameter of the disc. Thehead has a substantially dome-shaped surface overhanging the base. Step(a) includes molding the stems in molding cavities in a mold roll. Instep (b), the region extends from the terminal end towards the base adistance equal to from about 15 to 25% of the total distance from theterminal end to the base, or, in the special case of the convectionheating mentioned, up to about 30% of that distance. The contact surfacehas a surface finish selected from the group consisting of dimpled,smooth, textured, and combinations thereof. The surface finish comprisesdimples or other formations that are small relative to the size of thedisc or head, discrete and separated in both the X and Y directions andthe contact surface includes a density of dimples or other formationsper unit area of the contact surface that is greater than or equal tothe density of stems per unit area of the base and especially for thesaid small discrete formations for modifying the under-structure of thediscs through transformation of displacement through the thickness ofthe disc, the relatively small discrete formations number between about3 and 15 per disc or head. During step (c), the dimples are in at leastpartial registration with the stems.

In other aspects, the present invention employs a method of forming afastener that includes: (a) forming a plurality of stems extending froma common base to a terminal end structure from a thermoformablematerial; (b) heating a region of the terminal end structure to apredetermined softening temperature, to soften the material in theregion, while maintaining the remaining portion of the stems at atemperature lower than the softening temperature; and (c) contacting theterminal ends with a contact surface to form heads at the terminal endof the stems, at least a portion of the contact surface having asufficiently rough texture to impart a loop-engaging surface roughnessto at least a portion of the heads.

Preferred methods include one or more of the following features. Thecontact surface comprises the cylindrical surface of a roll. The contactsurface has a sandpaper-like texture. The contact surface has a surfaceroughness (rugosity) of about 10 to 200 microns. The contact surfacedefines a plurality of dimples. The contact surface includes a densityof dimples per unit area of the contact surface that is greater than orequal to the density of stems per unit area of the base. The surfaceroughness imparted to the heads is sufficient to increase the peelstrength of the fastener by from about 10 to 100%. The contact surfaceis so related to the thickness and nature of the heads being formed thatcontact with the upper surface of the heads is effective to transmit theeffect through the resin thickness of the heads sufficiently to impart adegree of texture or surface roughness to the peripheral edge of thehead or the undersurface of the head or both, in regions contacted byloops during hook-to-loop engagement. Preferably, the contact of theconforming surface with the head imparts discrete depressionsdistributed in X or Y or both directions and numbering in the rangebetween about 3 and 15 depressions per head.

According to some aspects of the invention there is a fastener elementincluding an elongated stem extending and molded integrally with asubstantially planar base, and a head disposed at a terminal end of thestem, at least a portion of the head having a rough surface having asandpaper-like surface texture.

Preferred fastener elements include one or more of the followingfeatures. The rough surface has a surface roughness (rugosity) of fromabout 10 to 200 microns. The rough surface has sufficient surfaceroughness to increase the peel strength of the fastener by from 10 to100%. The head is substantially disc-shaped or mushroom-shaped.

According to some aspects of the invention there is an attachment stripfor attaching a mesh screen to a surface. The attachment strip includes(a) a substantially planar base; (b) a plurality of elongated stemsextending from the base; and (c) a plurality of heads, each head beingdisposed at a terminal end of one of the stems. According to one aspectof the invention, at least a portion of the heads have a rough surfacehaving a sandpaper-like surface texture.

The term “softening temperature,” as used herein, refers to atemperature at which the thermoformable material can be formed by asurface pressed against it and includes the melting temperature as wellas lower temperatures at which deformation and flow of the material canoccur.

The term “disc-shaped”, as used herein, refers to a shape having top andbottom surfaces, at least a portion of the top surface beingsubstantially parallel to a corresponding portion of the bottom surface,and having a thickness that is substantially less than its equivalentdiameter. “Equivalent diameter” means (a) for a circular disc, theactual diameter, and (b) for a disc having a non-circular shape, thediameter of a circular disc having the same thickness and surface areaas the non-circular disc. When viewed from above, the disc-shape may besubstantially circular, irregular in shape but approximately circular,or non-circular, e.g., square or cross-shaped. The disc-shape may beflat, or may have other shapes such as domed, wavy, or pyramidal.

The term “mushroom-shaped”, as used herein, refers to any shape having adomed portion, with the exception of a complete sphere.

The phrase “loop-engaging surface roughness”, as used herein, means adegree of surface roughness that is sufficient to “catch” on a loopfastener element and provide a partial, momentary engagement therewith.

The term “sandpaper-like”, as used herein, means a surface roughnessakin to the surface texture of sandpaper.

The fastener elements of the invention have a head geometry thatadvantageously provides a strong attachment to a female fastenercomponent. The fastener elements are particularly well adapted for usein fastener tapes for attaching an insect screen to a window frame, asthe head geometry provides a strong engagement with the mesh of theinsect screen. Insect screen fastener tapes of the invention exhibitgood peel strength and thus good resistance to detachment due to wind.The methods of the invention allow the fastener elements to bemanufactured using a relatively simple and economical process.

Other and very important aspects of the present invention go beyondwindow screening to provide male fastener elements capable of improvedengagement with loops formed by fibers of thin nonwoven materials, orwith other open structures.

In one aspect of the invention, a method of forming a loop-engagingtouch fastener product includes forming, from a thermoformable material,a preform product having a sheet form base and an array of preform stemformations integral with and extending from the base to correspondingterminal ends, each of the stem formations including a first portionjoined to the base and a terminal second portion extending from thefirst portion to a terminal end, there being a discrete transition to alesser cross-sectional area in the second portion relative to the firstportion according to cross-sections taken parallel to the sheet-formbase; and deforming substantially all of the second portions of at leastsome of the stem formations to form, for each portion so deformed, anopening-engaging feature, especially a loop-engageable feature,overhanging the sheet-form base sheet while leaving the first portionsubstantially as-molded.

Preferred methods include one or more of the following features. Thediscrete transition begins at a distance from the sheet-form base atleast half way to the terminal end of the stem formation. The discretetransition includes a substantial decrease in the cross-sectional areaof the second portion relative to the first portion of the stemformation.

In another aspect, the invention provides a hook fastener preformproduct for subsequent formation of a loop-engaging hook fastenerproduct, the preform product including a base sheet having a surface ofthermoplastic resin; and a plurality of stem formations formedintegrally (i.e., monolithically) with the surface of the base toprotrude therefrom. Each of the protruding formations includes a first,stem portion intersecting the surface and a second portion extendingfrom the first portion to a distal end, to define a height of theformation relative to the surface. An intersection of the first andsecond portions occurs at a distance from the surface equal to at leasthalf the height of the formation, the intersection defining a discretetransition in structure of the formation, wherein the second portion isselected to improve the formation of the head or disc of the fastener,e.g., to be more susceptible to deformation energy than the stemportion, for instance being reduced in mass to form a disc or head ofreduced thickness, or to be more easily pre-conditioned for being formedinto a head, or to be formable into a head structure that has improvedloop engagement properties, especially resistance to peel when engagedwith loops formed by short or low lying fibers of a thin nonwoven loopmaterial. Variations of this aspect of the invention may include an areaof any cross-section of the second portion taken parallel to the surfacebeing less than an area of any cross-section of the stem portion takenparallel to the surface, or outermost (i.e., distal) cross-sectionshaving area less than half, or preferably less than one fourth or lessof the area of the first, stem portion.

In another aspect, the invention provides a hook fastener preformproduct for subsequent formation of a loop engaging hook fastenerproduct, the preform product including a base sheet having a continuouslength, a width and a surface of thermoplastic resin; and a plurality ofstem formations formed integrally with the surface to protrudetherefrom, each of the protruding formations including a first, stemportion intersecting the surface and a second portion extending from thefirst portion to a central peak to define a height of the formationrelative to the surface, wherein longitudinal edges of the secondportion are tapered relative to longitudinal edges of the first stemportion toward the central peak. Variations of this aspect of theinvention may include each stem formation having lateral edges thattaper from the first portion continuously to the terminal end of theprotruding formation, a stem having an “M” shape or an “A” frame houseconfiguration being examples, only.

In another aspect, the invention provides a hook fastener preformproduct for subsequent formation of a loop-engaging hook fastenerproduct, the preform product including a base sheet having a continuouslength, a width and a surface of thermoplastic resin; and a plurality ofstem formations formed integrally with the surface to protrudetherefrom, each of the protruding formations including a first stemportion intersecting the surface and a second portion extending from thefirst portion to define a height of the protruding formation relative tothe surface, wherein the second portion comprises a first peak along afirst longitudinal edge, a second peak along a second longitudinal edgeand a central valley devoid of resin therebetween.

Variations of this aspect of the invention may include each protrudingformation, e.g. in the form of a thin fin, having opposite lateral edgesthat taper continuously from the first portion to the terminal end ofthe formation, for instance, to describe the configuration of the letter“M.” In another case the preform product comprises effectively, one halfof the foregoing geometry, i.e., a peak is located at a firstlongitudinal edge of this fin and a relatively low region is at theopposite longitudinal edge. In preferred embodiments of this aspect, theprotruding formation has an “M” or an half “M” shape in which the heightof the formation decreases linearly from the one or both peaks to thelowest part of the top of the structure.

In another aspect, the invention provides a hook fastener preformproduct for subsequent formation of a loop engaging hook fastenerproduct, the preform product including a base sheet having a continuouslength, a width and a surface of thermoplastic resin; and a plurality ofstem formations formed integrally with the surface to protrudetherefrom, each of the stem formations including a first stem portionintersecting the surface and a second portion extending from the firstportion to define a height of the protruding formation relative to thesurface, wherein the first portion comprises a first cylindrical shapeof a first diameter, and the second portion comprises a secondcylindrical shape of a second diameter, the second diameter beingsmaller than the first diameter. Variations of this aspect of theinvention may include the second portion being concentric with the firstportion.

In the foregoing references to “second portion,” it will be understoodthat the second portion may itself be formed of multiple portions.

According to another aspect of the invention, a new way to manufacturehook products for these and other purposes is achieved by selection offorming conditions to form heads on pre-molded stems or protrudingstructures, that provide a localized molten mass of the hook resin suchthat the action of surface tension on the molten mass causes the mass toso overhang a cross-machine extremity of the distal end of the stem,that, when deformed by a conforming surface, such as that of a formingroll, the molten resin is formed into a generally flattened, thin headat a cross-machine extremity of the stem. In preferred embodiments,non-contact heating action melts the distal ends of the preformedstructures, and the forming surface is maintained at a lower temperaturethan that of the molten resin. Also in preferred embodiments, thesurface of the forming roll carries molding formations that produceirregular edges or contours to the heads being formed that promoteengagement and holding of fiber loops after engagement.

According to another aspect of the invention, a method of manufacturinga hook component for a hook and loop fastener is provided comprising (a)providing a continuous length of a preform stem component ofthermoformable resin, the component having a base layer from whichextend a plurality of preformed stems with thermoformable extremities ofpredetermined geometry, the stem component having a machine direction,(b) heating said deformable extremities of said stems to provide on eacha localized molten mass of resin which, under action of surface tension,so resides on the respective stem as to overhang a cross-machineextremity of the stem, and (c) deforming the molten mass with a formingsurface in manner to produce a generally flattened, thin head at thecross-machine extremity of the stem, (d) steps (a), (b) and (c) being soconducted as to produce a loop engageable head defining, in a plan view,a general contour having a peripheral arc AB parallel to the base of thepreform component, the head having an overhang aspect ratio OAR, definedas the ratio of the chord of the arc AB and the height “h” of the lineperpendicular to said chord lying at the furthest point of the arc fromthe chord, OAR=AB/h, where the chord of the arc lies in the plane whichdefines the cross-machine extremity of the stem and is parallel to saidmachine direction, the chord lying in or being tangent to the surface ofsaid stem that defines the cross-machine extremity of the stem, saidaspect ratio OAR being less than 3.5, preferably about 2.

According to another aspect of the invention, a hook component for ahook and loop fastener is provided comprising a base layer from whichextend a plurality of stems having respective loop-engageable heads, atleast some of the heads each having a general contour, in plan view,that has a peripheral arc AB parallel to the base, the head having anoverhang aspect ratio OAR, defined as the ratio of the chord of the arcAB and the height “h” of the line perpendicular to said chord lying atthe furthest point of the arc from the chord, OAR=AB/h, where the chordof the arc lies in the plane which defines the cross-machine extremityof the stem and is parallel to said machine direction, the chord lyingin or being tangent to the surface of said stem that defines thecross-machine extremity of the stem, said aspect ratio OAR being lessthan 3.5, preferably about 2.

The foregoing method or the hook component may have one or more of thefollowing features.

The head has a vertical head thickness, down to its loop engagingregion, of no more than about 0.015 inch.

The combined height of each stem and its respective head, measured fromthe base layer, is no more than about 0.055 inch.

The footprint area of each head is no more than about 4.30×10⁻⁴ squareinch.

The stem preform comprises a thin fin projecting from said base, saidthin fin having a cross-machine component of orientation of at leastabout 45 degrees, the fin characterized by a length from thecross-machine extremity of the projection, along the length of theprojection, that is greater than about twice the thickness of the fin,the length and thickness being measured at right angles in a planeparallel to the plane of the base of the hook component.

Another aspect of the invention is a hook component for a hook and loopfastener comprising a base layer from which extend a plurality of stemshaving respective loop-engageable heads, the heads overhanging across-machine extremity of the respective stems, the component having amachine direction, the stem comprising a thin fin projecting from saidbase, said thin fin having a cross-machine component of orientation ofat least about 45 degrees, the fin characterized by a length from thecross-machine extremity of the projection, along the length of theprojection, that is greater than about twice the thickness of the fin,the length and thickness being measured at right angles in a planeparallel to the plane of the base of the hook component.

Methods or products featuring the thin fin may have one or more of thefollowing features.

The length of the fin is at least 2½ times its thickness.

The length of the thin fin extends in the cross-machine direction.

The stem preform, or the stem, as the case may be, is double-ended,there being a said length of thin fin extending inwardly in oppositedirections from cross-machine extremities on opposite ends of the stempreform or stem.

According to other aspects of the invention, it is further found thatimportant special geometries of molded preform elements, and selectedtechniques of head forming, are effective in achieving importantadvantages in this context, and more generally.

According to one particularly important aspect of the invention, themolded stem preform comprises a thin fin projection having a significantcross-machine component of orientation, the thin fin characterized by alength from the cross-machine extremity of the projection, along thelength of the projection, that is greater than about twice the lengthand thickness being measured at right angles in a plane parallel to theplane of the base of the hook component, preferably, such length beingin the range of about 2½ times such thickness, to less than 3 times suchthickness.

Maximum length of the fins is not dictated by melted configurationconsiderations.

Preferred aspects of this aspect have one or more of the followingfeatures.

A stem preform is double-ended, in that there is such a length of thinfin extending inwardly in opposite directions from cross-machineextremities on opposite ends of the preform member. The stem preform hasa stiffening feature that serves to stiffen the preform from columnarcollapse during application of postforming force. In certain preferredembodiments the stiffening feature has a height that is less than thatof the thin fin, such that, in some embodiments, it is not reformedduring the post-forming action, or, in other embodiments, is notreformed to the degree to which the cross-machine extremity of the thinfin is reformed. In other embodiments, the strengthening projectionitself comprises a thin fin having a length greater than about twice itsthickness, or more, measured in the same manner as above, and preferablyhas the other preferred attributes of thin fins mentioned above. Incertain preferred embodiments, the stem has multiple thin fins, forinstance it is of cross or plus sign form, having four projections froma central region, or it can have, e.g., three or five projections, eachhaving the described thin fin form. In some cases the pairs ofoppositely extending fins are aligned with the cross-machine and machinedirections, while in other embodiments all projections form acute angleswith those directions.

Another important feature of the invention is a thin fin stem preform asdescribed which has its direction of elongation set at an acute angle tothe machine direction, for instance 30 or 45 degrees, but has an endsurface at its cross-machine extremity that is generally aligned withthe machine direction. In certain preferred embodiments thiscross-machine extremity is defined by a planar end face that isperpendicular to the base of the hook component and aligned with themachine direction, preferably this fin-shaped preform element havinglong sides that are generally of planar, parallel form, the preformterminating at one corner at the cross-machine extremity with ahorizontal profile included angle of substantially less than 90 degrees,for instance 45 degrees. In certain preferred embodiments, thehorizontal cross-section of the entire stem is of parallelogram form, inwhich each cross-machine extremity of the profile ends in a stem portiondefining an included angle of substantially less than 90 degrees, e.g.as little as 45 degrees. In another embodiment, the profile of the stemis defined as two thin fins of such profile, set at substantial anglesto each other, e.g. at 90 degrees, to form a cross of the twoparallelograms. In other cases an X, Y array of such preform elementsincludes bands in which the parallelogram profiles have a firstorientation and bands, preferably bands alternating with thefirst-mentioned bands, having the opposite or mirror image orientation.

Another aspect of the invention employs a thin fin preform element,which, at least in the cross machine direction, has the profile of an“M” with vertically straight sides at the cross-machine extremities,and, effectively a “V”-shaped cut out in its central region that isdevoid of resin, so that the outermost portions of the preform elementare tapered from an outward point to horizontal cross sections ofincreasing area moving toward the base. With this form, as meltingprogresses, as when heated by a non-contact heat source, the moltenresin preferentially flows over the edge of the straight side to form amolten mass overhang at the cross-machine extremity. This mass later isformed to provide the desired loop-engaging shape.

In preferred embodiments of these aspects: non-contact heating isaccomplished principally by convection heating, preferably by the hotgaseous combustion products of a close-approaching gas flame; theforming surface that engages the molten surface has a molding surfacethat imparts a degree of roughness or shaped profile to the outersurface at the peripheral edges of the head that is formed, of size andshape enabling telegraph of the disturbance through the mass of theoverhanging portion to provide a degree of irregularity, texture orroughness on loop-engaging surfaces of the overhanging head, forinstance the peripheral edges of the head's under-surfaces, that promoteretention of the loop on the hook under peel conditions.

Other aspects of the invention comprise hook manufacture employing stempreform products of the geometries described, employing non-contactheating, enabling formation of advantageously sized and/or locatedrounded masses of molten resin, followed by engagement of the masseswith a forming surface.

In preferred embodiments a step is employed to prevent sticking oradherence of the formed head to the forming surface duringdisengagement. Embodiments of the invention include maintaining theforming surface cooler than the ambient boiling or condensationtemperature of water and introducing water or steam to that surface. Inone important embodiment, the mode of non-contact heating is byimmersing the terminal end portions of the formations in the flow of hotcombustion products of a close-approaching gas flame in such manner thatwater of combustion condenses on the cooled forming roll and performs ananti-adhesion function.

Another aspect of the invention involves “superheating” a preformelement by a non-contact heat source in advance of press-forming theheated resin mass with a relatively cool forming surface, such that,following such press forming, under the influence of gravity and/orsurface tension, further forming movement of the resin occurs beforestabilizing, e.g. to form a self-engaging male fastener formation, as inthe case of mushroom formations, or a loop engaging structure, as in thecase of heads with a “J” profile.

In preferred embodiments the amount of such “superheating” in relationto heat loss at the forming surface, which is preferably a cooled roll,ensures that the retained heat maintains the resin sufficiently heatedto enable the mass to flow into the form of a mushroom, or in otherembodiments, is sufficient to enable peripheral portions of the formedmass to droop or self-deform to form a “J” like profile, beforesolidifying.

In preferred embodiments of this feature the resin for thus forming amushroom structure following press-formation is low density polyethyleneor other resin having a low heat-deflection temperature, and for soforming a “J” like profile, the resin is high density polyethylene ornylon or resins of similar higher heat deflection temperatures.

Another important aspect of the invention is the realization that theproperty of molecular orientation of the resin of preformed stemsintended for subsequent heat forming, contrary to thought of others isnot a necessity and indeed can advantageously be avoided with desirableeffects. It is realized that pre-heating a non-oriented resin projectionenables a mass of molten resin to form as a ball, dependent on the sizeand shape of the resin formation melted, and that the physical locationof this ball can be advantageously selected and controlled by pre-designof the protruding structure, so that a subsequent press forming (i.e.flat-topping) of the molten resin can distribute the resin to a desiredfinal shape; or a desired distribution geometry, in the case ofsuper-heated resin, such that gravity and/or residual surface tensioneffects accomplish a further desired deformation. In certain situations,further cooling, or even further surface pressing can be employed fordetermining the final shape.

In preferred embodiments, the sequence is preheating to super-heatcondition by convection, preferably by immersion in combustion productsof a gas flame, flat-topping with a cooled roll to produce a desiredareal distribution of the resin, and allowing the elements to furtherform from the distributed shape by action of gravity and surfacetension. This is followed by air cooling or engagement with a furthercooled roll. In some cases, at this point, the product may be engaged bya heated roll to finalize the conformation or surface texture of theproduct.

Another aspect of the invention concerns convection heating of preformelements, employing a distributed gas flame. The luminescent flame ispositioned to immerse side surface of terminal portions of the preformelements as well as the end surfaces, in hot combustion products of thegas flame, at temperature of the order of 1000° C., to achieve rapidheating of the elements and enable the elements to proceed at highproduction rate through the subsequent press forming (or “flat-topping”)stage.

In preferred embodiments the press forming surface is maintained at atemperature below condensation temperature of water, in preferred casesin the range of between about 5° and 60° C., preferably 10° and 45° C.and most preferably of about 25° and 30° C., and the surface is exposedto the combustion products of the flame to cause condensation of waterover the forming surface in quantity to enhance release of the resinfrom the forming surface after the forming action. Preferably theforming surface is a chilled conforming or pressing roll.

In the case of using a heated pressing roll following preheating withconvection heating as described, anti-adhering material is provided atthe interface between the forming surface and the resin. In preferredembodiments the material comprises a Teflon or other anti-stick coatingof the forming surface, injection of water or steam to the interface, orboth. In this manner, the speed of operation of the process may beincreased while still using developed tooling that employ hot rolls orother heated forming surfaces.

In yet another aspect of the invention, a method of forming a loopengaging fastener product includes providing a preform stem producthaving a plurality of stems, each of which rises from a base to a distalend and contacting the distal end of at least some of the stems with anultrasonic horn to form loop engaging heads.

Variations of this aspect of the invention may include one or more ofthe following features. The ultrasonic horn is rotating while contactingthe distal end of at least some of the stems. The preform stem productis introduced between a gap formed by the ultrasonic horn and an anviland the gap is sized to cause the distal ends of at least some of thestems to contact the rotary horn. The anvil is rotating.

The details of one or more embodiments of the invention are set forth inthe accompanying drawings and the description below. Other features,objects, and advantages of the invention will be apparent from thedescription and drawings, and from the claims.

DESCRIPTION OF DRAWINGS

FIG. 1 is a side view of a fastener including a fastener elementaccording to one embodiment of the invention. FIG. 1A is a top view ofthe fastener element, with the stem portion shown in phantom lines.FIGS. 1B, 1C and 1D are top views of fastener elements according toalternate embodiments of the invention; these fastener elements have thesame profile, when seen from the side, as that shown in FIG. 1.

FIG. 2 is a side cross-sectional view of a fastener element according toan alternate embodiment of the invention. FIGS. 2A and 2B are top viewsof fastener elements according to alternate embodiments of theinvention; these fastener elements have the same cross-sectional shapeas that shown in FIG. 2.

FIGS. 3 and 3A are side cross-sectional views of fastener elementsaccording to other alternate embodiments of the invention. FIGS. 3B and3C are perspective views of fastener elements according to otheralternate embodiments of the invention.

FIG. 4 is a front view showing a fastener element of FIG. 1 or FIG. 2engaged with the mesh opening of an insect screen.

FIG. 5 is a schematic side view of a machine for manufacturing afastener element.

FIG. 6 is an enlarged view of a portion of the machine shown in FIG. 5.

FIG. 7 is an enlarged side detail view of area A in FIG. 6, showing aportion of the stem-carrying base prior to conformation. FIG. 7A is ahighly enlarged view of one of the stems shown in FIG. 7. FIG. 7B is atop view of the portion of the base shown in FIG. 7A.

FIG. 7C is a plan view of the preform product comprising an array of thestems proceeding in the machine direction.

FIGS. 8-8D are side views showing various suitable conformation rollsurfaces for forming fastener elements of the invention.

FIGS. 9A and 9B are further magnified side and front views,respectively, of an individual stem formation of the preform stemproduct of FIGS. 7-7C.

FIGS. 10A, 10B and 10C are unscaled, magnified side, front and top viewsof a loop engaging fastener product formed from the preform stem productof FIGS. 7-7C.

FIGS. 11A, 11B and 11C are further magnified front, side and top viewsof an individual loop engaging fastener element of the loop engagingfastener product of FIGS. 10A-10C.

FIG. 12 is a schematic illustration of a method and apparatus forforming the preform stem product of the FIGS. 7-7C and for subsequentlyforming the loop engaging fastener product of FIGS. 3A-3C from thepreform stem product in an in-line process.

FIG. 13 is a schematic illustration of an alternative method for formingthe loop engaging fastener product of FIG. 12.

FIG. 13A is a perspective diagram showing the path of travel of a rotaryultrasound horn parallel to the machine direction.

FIG. 13B is a perspective diagram showing a rotary ultrasonic horn, theaxis of which extends perpendicular to the machine direction and theplane of the web of the preform elements.

FIG. 14 is a schematic illustration of an alternative apparatus andmethod for forming the preform stem product of FIGS. 7-7C.

FIGS. 15A and 15B are side and front views, respectively, of anotherpreform stem formation.

FIGS. 16A, 16B and 16C are side, front and top views, respectively, of aloop engaging fastener element formed from the preform stem formation ofFIGS. 15A and 15B.

FIGS. 17A and 17B are side and front views, respectively, of anotherpreform stem formation.

FIG. 17C is view similar to that of FIG. 17A, but illustrating amodified preform stem formation.

FIG. 17D is a cross-sectional view of tooling for forming the preformstem formation of FIG. 17C.

FIGS. 18A, 18B and 18C are side, front and top views, respectively, of aloop engaging fastener element formed from the preform stem formation ofFIGS. 17A and 17B.

FIGS. 19A and 19B are side and front views, respectively, of anotherpreform stem formation.

FIGS. 20A, 20B and 20C are side, front and top views, respectively, of aloop engaging fastener element formed from the preform stem formation ofFIGS. 19A and 19B.

FIGS. 21A and 21B are side and top views of another preform stemformation.

FIG. 22 is a side view of a loop engaging fastener element formed fromthe preform stem formation of FIGS. 21A and 21B.

FIG. 23 is a diagrammatic perspective view of an embodiment of amulti-lobed hook element made according to the invention, while FIG. 23Ais a side view taken on lines 23A-23A of FIG. 23 and FIG. 23B is a topview taken on lines 23B-23B of FIG. 23A.

FIGS. 23C through 23E are views of a preform element employed in formingthe hook element of FIG. 23, FIG. 23C being a diagrammatic perspectiveview of the molded preform element, FIG. 23D a vertical side view of theelement and FIG. 23E a horizontal section view of the preform elementtaken on line 23E-23E of FIG. 23D.

FIG. 23F is a side view similar to FIG. 23A of the stem after it haspassed by non-contact heat source, before reaching the conforming roll,while FIGS. 23F-A through FIGS. 23F-E is a set of figures thatillustrates the “balling” of melted resin along the exposed edge of asingle thin fin element as a result of convection preheating by a gasflame.

FIG. 23G is a diagrammatic side view of a forming machine, and 23H is amagnified diagrammatic view of the heading action of the machine. FIG.23G′ is a side view and FIG. 23G″ is a perspective view of a preferredconfiguration of the machine.

FIGS. 23I and 23J are highly magnified partial cross-sectional viewstaken parallel to the periphery of respective mold rings for forming thepreform element of FIG. 23 while FIGS. 23L and 23M are more highlymagnified cross-sections taken on lines 23L-23L and 23M-23M of FIGS. 23Iand 23J, respectively.

FIG. 23K is a view similar to FIGS. 23I and J, of the two mold ringsheld face-to-face together in registry to form a plus-form mold cavity,to mold the element of FIG. 23.

FIGS. 23N and 23O are still further magnified views of two assemblypatterns achievable with the set of mold rings of FIGS. 23I and J,assembled with intervening spacer rings.

FIGS. 23P and Q are top and side diagrammatic views of a fastener formedfrom a square-profile cross-section stem. FIG. 23R is a vector diagramrepresenting forces applied between a hook and a loop; FIGS. 23S and 23Tare views similar to FIGS. 23P and 23Q of a hook formed by a thin finpreform stem while FIG. 23U is a vector diagram for the hook of FIGS.23S and 23T, of form similar to that of FIG. 23R. FIGS. 23V and W aresimilar to FIGS. 23Q and 23R, respectively, for a hook subjected to pullfrom a loop at an angle and FIG. 23X is a comparison of angle Φ andθ_(min), over an angular range. FIG. 23Y is a diagram showing hook andloop components being peeled from each other.

FIG. 24 is a diagrammatic perspective view of a second embodiment of asingle hook element made according to the invention, while FIG. 24A is aside view of the element of FIG. 24 and FIG. 24B is a top view taken onlines 24B-24B of FIG. 24A.

FIGS. 24C through 24E are views of a preform element employed in formingthe hook element of FIG. 24, FIG. 24C being a diagrammatic perspectiveview of the molded preform element, FIG. 24D a vertical side view andFIG. 24E is a horizontal section view of the preform element taken online 24E-24E of FIG. 24D.

FIG. 25 is a top view of another embodiment of a single hook madeaccording to the invention, while FIG. 25 a is a top view of the preformemployed to produce the embodiment of FIG. 25 and FIGS. 25B and 25C areside views of the preform taken respectively on lines 25B-25B and25C-25C of FIG. 25A. FIG. 25D is a plan view of another embodiment,similar to that of FIG. 25, but with the Y dimension fins at theextremities of the machine direction structure.

FIGS. 26 and 26A are side and top views of another embodiment whileFIGS. 26B and 26C are side and top views of a preform element used informing the embodiment of FIGS. 26 and 26A.

FIGS. 27 and 27A are, respectively, plan and side views of anotherembodiment, while FIG. 27B is a top view of the preform element fromwhich the embodiment of FIGS. 27 and 27A is fabricated.

In the same respect as embodiments above, FIGS. 28, 28A and 28Billustrate another embodiment.

FIGS. 29, 29A, 29B and 29C depict dome shaped mushrooms formed followingflat-topping by flow of previously “super heated” polyethylene (FIGS. 29and 29A referring to use of low density polyethylene) while FIG. 29Dillustrates use of two such components as a self-engaging fastener.FIGS. 30 and 31 depict the forming of J configurations by post-formingflow, resulting from use of resins of different flow properties, nylonand high density polyethylene, respectively.

FIGS. 32, 32A and 32B, illustrate another embodiment of a quadrolobalhook, featuring J profile formation.

FIGS. 33, 33A and 33B illustrate a quadrolobal M hook while FIGS. 33C, Dand E illustrate the molded preform product from which it is fabricatedand FIG. 33F illustrates the condition of the terminal end of thepreform of FIG. 33D after non-contact heating and before flat topping.FIGS. 33G, H and I are cross-sectional views as noted that illustratemold tooling for molding the preform element of FIG. 33.

FIGS. 34, 34A and 34B illustrate in the usual manner another embodiment,based on a single M-shaped preform and FIGS. 34C, 34D and 34E illustratethe molded preform product from which it is formed, while FIG. 34A′illustrates a hook profile similar to FIGS. 34A, but formed in adifferent manner.

FIG. 34F through FIG. 34J are various cross-sections taken through moldrings of the set as indicated, that define molds for molding the preformstem component of FIGS. 34C, D and E.

FIGS. 35-35E are views corresponding to FIGS. 34-34E of anotherembodiment, a modified M, and its preform element, while 35A′illustrates a hook profile similar to FIG. 35A but formed in a differentmanner.

FIGS. 36-36E are similar views of an N hook and its preform element,while FIG. 36A′ is a hook profile similar to FIG. 36A but formed in adifferent manner.

FIG. 37 is a diagrammatic perspective view of a further embodiment of asingle hook element made according to the invention, while FIG. 37A is aside view of the element and FIG. 37B is a top view taken on lines37B-37B of FIG. 37A.

FIGS. 37C through 37E are views of a preform element employed in formingthe hook element of FIG. 37, FIG. 37C being a diagrammatic perspectiveview of the molded preform element, FIG. 37D a vertical side view of itand FIG. 37E a horizontal cross-section view of the preform elementtaken on line 37E-37E of FIG. 37D.

FIGS. 37F and G are cross-sections of mold tooling for molding avariation of the element of FIG. 37C, that includes a supportingpedestal.

FIG. 37H is a plan view of a male fastener component comprising an X, Yarray of the male fastener elements of FIG. 37, while FIGS. 37I and Jare diagrammatic perspective views of the array of FIG. 37H.

FIGS. 38 and 38A are diagrams showing the relationship of the chord ABat the stem face relative to the disk overhang in the case of square andcylindrical stems, represented by an overhang aspect ratio, while FIG.38B illustrates the different ratio obtainable with a thin fin stem andFIGS. 38C and 38D illustrate, by two examples, the differentrelationship obtainable employing the principles of constructiondescribed in relation to FIGS. 37-37A.

Like reference symbols in the various drawings indicate like elements.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to FIG. 1, fastener 10 includes a base 12 and a fastenerelement 14 extending from the base. (Fastener 10 generally includes anarray of fastener elements; a single fastener element is shown forclarity.) Fastener element 14 includes a stem 16 and, at the terminalend of stem 16, a head 18. Head 18 is shaped for engagement with anotherfastener component, for example a female fastener component having aplurality of loops, a mesh such as an insect screen, or another fastenercomponent similar to fastener 10.

As shown in FIG. 1, head 18 is substantially disc shaped, including asubstantially planar top surface 20, and a substantially planar bottomsurface 22 that faces and overhangs base 12. It is desirable that thedisc be relatively thin, allowing a cooperating fastener element, e.g.,a loop or the wire mesh of a window screen, to penetrate into the discby flexing the disc material. Preferably, the thickness of the disc isfrom about 5 to 15% of the equivalent diameter of the disc. If the discis thinner, it will tend to have reduced cycle life (i.e., durabilityduring repeated engagement and disengagement of the fastener), whereasif the disc is thicker the fastener may exhibit reduced peel strength.As shown in FIG. 1A, head 18 is substantially circular when viewed fromabove, and stem 16 is substantially circular in radial cross-section, asshown, or square in radial cross-section. (In other embodiments, head 18can be irregular in shape (FIG. 1B), square (FIG. 1C) or cross-shaped(FIG. 1D) when viewed from above.) The disc shape is particularlyadvantageous for engagement with a mesh screen (FIG. 4) because thesides 25 of the mesh opening can penetrate into the thin disc. As aresult, as shown in FIG. 4, secure engagement can be provided eventhough the disc is smaller than the mesh opening and only engages one ortwo sides 25 of the mesh opening. The head 18 is also suitable forengagement with loops or with other similarly shaped heads.

In an alternate embodiment, shown in FIG. 2, head 18 includes a domedportion 24, and a correspondingly dome-shaped lower surface 23, a majorportion of which is substantially parallel to domed portion 24. Surface23 faces and overhangs base 12, providing a surface for engagement witha female fastener element or mesh. Head 18 can have various shapes. Forexample, head 18 can be a disc that is square or rectangular when viewedfrom the top (FIG. 2A), with two opposed edges of the disc being bentdown to form a U-shaped domed portion. Alternatively, head 18 can be acircular disc that is bent down around its periphery to form amushroom-like domed portion. These head shapes are particularlyadvantageous for engagement with a mesh screen (FIG. 4) because thedomed portion allows smooth penetration into the mesh openings 27 andthe thin disc shape allows sides 25 of the mesh opening to be embeddedinto surface 23. Head 18 can also be used to engage the loops of afemale fastener component, or to self-engage with another fastenerhaving similarly shaped heads.

In alternate embodiments, shown in FIGS. 3 and 3A, the disc-shaped headsare “wavy”. The head 18 may be S-shaped in cross-section, as shown inFIG. 3, or may be W-shaped, as shown in FIG. 3A. The head shapes shownin these figures may be provided with a rough surface, as describedbelow with reference to FIG. 3B.

In another alternate embodiment, shown in FIG. 3B, head 18 includes arough, sandpaper-like surface 30. Preferably, the texture of surface 30resembles that of 320 grain sandpaper (used for sanding metals). Thesandpaper-like surface includes protrusions that tend to catch on thefastener component with which the head 18 is engaged (not shown), makingit more difficult to inadvertently disengage the mated fastenercomponents. As a result, the strength of engagement is generallyincreased, relative to the strength obtained from a similar fastenerelement having a smooth surface. In particular, in preferred embodimentsthe peel strength, as measured by ASTM D 5170-91 (“T” method), isincreased by about 10 to 100%. It is preferred that the surface 30 havea surface roughness (rugosity) of at least 10 microns, more preferablyfrom about 10 to 200 microns.

In another embodiment, shown in FIG. 3C, the head 18 is pyramidal inshape. Preferably, the surface of the head that overhangs the base hasthe same contour as the upper surface of the head, so that a majorportion of the surfaces is substantially parallel.

In all of the embodiments shown in FIGS. 1-3C, the head overhangs thebase to a significant extent. Preferably, the surface area A1 of thesurface overhanging the base is equal to at least 20% greater than thesurface area A2 of the radial cross-section of the stem 16 taken alongline A-A, i.e., where the stem intersects the head. The surface area A1may be up to 600% greater than the surface area A2. For example, for afastener element in which surface area A2 is 0.03 mm², surface area A1is preferably about 0.05 mm². It is also generally preferred that theamount of overhang be substantially uniform around the perimeter of thestem, to provide a multi-directional engagement. However, for ease ofmanufacture it will in some cases be preferred that the amount ofoverhang be non-uniform, as will be discussed below with reference toFIG. 5.

A machine 100 for forming the fastener elements described above is shownin FIG. 5. A supply roll 102, 126 introduces a continuous supply of astem-carrying base 12 (shown in FIGS. 7-7B) into the machine 100.Stem-carrying base 12 is formed of a thermoformable polymer. In aprevious manufacturing step, roll 102 was wound up as the take-up rollat a molding station (not shown) at which stems 104 (FIGS. 7-7B) wereintegrally molded onto base 12. The molding station may include a moldroll having a plurality of mold cavities provided by aligned plates,e.g., as described, for example, by U.S. Pat. No. 4,794,028, thedisclosure of which is incorporated herein by reference, or may utilizeany desired stem-molding technique. As shown in FIG. 7B, the stems maybe rectangular or square in radial cross-section, if a rectangular orsquare head is desired, or may be oval, round, cross-shaped, or anyother desired shape, for forming similarly shaped heads (see FIGS.1A-1D).

The supply roll 102 is unwound by drive mechanism 106, which conveysstem-carrying base 12 into optional pre-heating area 108 which raisesthe temperature of the stem-carrying base 12 to a pre-heat temperaturethat is above room temperature but much lower than the Vicat temperatureof the polymer. This pre-heating allows the tips of the stems to beheated to a predetermined softening temperature more quickly during thenext step of the process.

Next, the base 12 moves to heating device 110, which heats a portion ofthe stems. As indicated in FIG. 7A, only a portion P of the stems 104,adjacent their tips 109, is heated by heating device 110, leaving theremainder of the stem relatively cool and thus relatively rigid.Preferably, the length L of portion P is less than 30% of the totallength L1 of the stem, more preferably from about 15% to 25% of L1.Portion P is heated to a softening temperature at which portion P can beformed into a desired head shape, typically a temperature that isgreater than or equal to the Vicat temperature of the thermoformablepolymer. The remainder of the stem is not heated, and remains at atemperature that is less than the softening temperature S, preferably atleast 10% less.

To ensure that only portion P is heated to the softening temperature, itis preferred that heating device 110 include a non-contact heat source111 (FIG. 6) that is capable of quickly elevating the temperature ofmaterial that is very close to the heat source, without raising thetemperature of material that is relatively further away from the heatsource. Suitable non-contact heat sources include flame heaters,electrically heated nichrome wire, and radiant heater blocks. To heatportion P to the softening temperature without contact, the heat sourcetypically must be at a relatively high temperature. For example, if thesoftening temperature is from about 100 to 140 C, the temperature of theheat source will generally be from about 300 to 1000 C and the heatsource will be positioned from about 0.1 to 30 mm from the tips of thestems.

After portion P of the stems has been heated, the base 12 moves toconformation head 112, at which base 12 passes between conformation roll114 and drive roll 116. Conformation roll 114 forms the portion P of thestems into a desired head shape, as will be described in further detailbelow, while drive roll 116 advances base 12 and flattens it againstroll 114 to enhance head uniformity. It is preferred that thetemperature of conformation roll 114 (the forming temperature) be lowerthan the softening temperature. Maintaining the conformation roll 114 atthis relatively low temperature has been found to allow the conformationroll to flatten the spherical (“ball-shaped”) heads that are generallyformed during the previous heating step into a desired head shape.Spherical heads are generally undesirable, as such heads tend not toprovide secure engagement with a mating fastener. A low formingtemperature also prevents adhesion of the thermoformable polymer to theconformation roll. Generally, to obtain the desired forming temperatureit is necessary to chill the conformation roll, e.g., by running coldwater through a channel 115 in the center of the roll, to counteractheating of the conformation roll by the heat from portion P of thestems. If further cooling is needed to obtain the desired formingtemperature, the drive roll may be chilled in a similar manner.

The surface texture of conformation roll 114 will determine the shape ofthe heads that are formed. If disc-shaped heads having a smooth surfaceare desired, the surface texture will be smooth and flat. If asandpaper-like surface is desired, the surface texture of theconformation roll will be sandpaper-like (FIG. 8). If mushroom-shaped(domed) heads are desired, the conformation roll will include aplurality of substantially hemispherical indentations (“dimples”) toform the dome portion of the heads (FIG. 8A). Disc-shaped heads having a“wavy” shape, e.g., as shown in FIGS. 3 and 3A, can be formed using theconformation roll surfaces shown in FIGS. 8B and 8C. The diamond-latticeconformation roll surface shown in FIG. 8D will give the head apyramidal shape, e.g., as shown in FIG. 3C. The conformation roll mayalso have a soft surface (not shown), e.g., rubber, to provide amushroom-shaped head.

Preferably, when the surface texture includes dimples, the density ofthe dimples is substantially uniform over the roll surface, and isgreater than or equal to the density of stems on the base 12. To allowfor improper registration between the stems and the dimples, it ispreferred that the density of the dimples be substantially greater thanthe density of the stems (if the density is equal, improper registrationmay result in none of the stems being contacted by dimples).

As discussed above, while the uniformly overhanging, domed head shapeshown in FIG. 2 is generally preferred, obtaining this shape may undulycomplicate manufacturing, due to the need to maintain substantiallycomplete registration between the dimples and stems. As a result, forease of manufacturing it may in some cases be desirable to form lessuniform head shapes by allowing the dimples and stems to be in partialregistration, rather than full registration. In these cases, theconformation roll should have a density of dimples that is significantlyhigher than the density of stems, to increase the probability of contactbetween the dimples and stems. In this manner, some of the heads arelikely to have the shape shown in FIG. 2, while other heads will havedifferent head shapes resulting from contact of a stem with a portion ofa dimple.

The spacing of the conformation roll 114 from the drive roll 116 isselected to deform portion P of the stems to form the desired headshape, without excessive damage to the unheated portion of the stems. Itis also preferred that the spacing be sufficiently small so that thedrive roll flattens base 12 and provides substantially uniform contactpressure of stem tips 109 against the conformation roll. Preferably, thespacing is approximately equal to the total height of the stem (L1, FIG.7A) less the length of the heated portion P (L, FIG. 7A).

Next, the base 12 moves to a cooling station 118. Cooling station 118cools the formed heads, e.g., by cool air, preventing furtherdeformation of the heads. Preferably, the heads are cooled toapproximately room temperature. The cooled base is then moved throughdriving station 520 and wound onto take-up roll 522 by winding element524.

Alternate supply and take-up rolls 126, 128 are provided so that whensupply roll 102 is depleted and/or when take-up roll 524 is filled, theappropriate roll can be easily replaced without disrupting the process.

Suitable materials for use in forming the fastener are thermoplasticpolymers that provide the mechanical properties that are desired for aparticular application. Preferred polymers include polypropylenes, suchas those available from Montell under the tradename MOPLEN,polyethylenes, ABS, polyamides, and polyesters (e.g., PET).

Other embodiments are of course possible.

For example, while disc-shaped heads have been shown and discussedabove, the head may have any desired shape that provides a surfaceoverhanging the base to an extent sufficient to provide amulti-directional engagement having desired strength characteristics.

Moreover, while the process described includes only a single heating ofthe stem tips and a single pass through a conformation head, these stepsmay be repeated one or more times to provide other head shapes.Subsequent conformation heads may have the same surface as the firstconformation head, or may have different surfaces.

In addition, if desired, the stem tips may be cooled after the heatingstep and immediately before the conformation head, to form a sphericalhead that is then forced down against the stem, embedding the upperportion of the stem in the head to form a mushroom-shaped head.

Further, in some cases it is not necessary to cool the conformationroll. If the desired head shape can be obtained and resin sticking canbe avoided, the conformation roll may be used without either heating orcooling, or may be heated.

As illustrated in FIGS. 7, 7A, 7B and 7C, one example of a preformproduct 9 for producing a fastener product, has a flexible, yetrelatively planar base sheet 12 from which stem formations 104 project.Stem formations 104 are formed integrally, i.e. monolithically from thesame thermoplastic resin, e.g., polypropylene, as the surface 13 of basesheet 12 from which they project. As shown in the more detailed views ofFIGS. 9A and 9B, each stem formation 104 has front and back edgesurfaces 101, 103 that typically taper very slightly (e.g. 1°, notshown), and fairly continuously from broadly radiused intersectionsurfaces 15 with base surface 13 to a distal end 109 of the stemformation. Side edge surfaces 107 are relatively perpendicular to thebase and extend to distal end 109, which is relatively parallel to thebase. The slight taper or draft angle of front and back edge surfaces101, 103 aids in the removal of the stem formations from the moldcavities in which they are formed.

In the example of FIGS. 9A, 9B, the stem formations have an overallheight, L₁, from base surface 13 to distal end 109, a constant width, w,between the side surfaces 107 and a length, 1, as measured between thetop of the tapered front and back surfaces.

In one example, dimensions w and 1 are equal, e.g. 0.008 inch, toprovide a stem of square cross-sectional profile, in which case theheight L₁ may be e.g. 0.027 in.

Referring now to FIGS. 10A-10C, the preform product can be formed, asfurther described below, into a fastener product 10 having the same basesheet 12 and surface 13, but with the tips of the stem formationsflattened relative to the base to form loop engageable heads 18. Eachengageable head 18 is generally disc-shaped and extends outward from itsrespective stem portion 16 to overhang and oppose base surface 13. Asillustrated more clearly in FIGS. 11A-11L, discs 18 are slightlyoval-shaped, having a major diameter J, in the example, of the order of0.017 inches, extending in the direction corresponding to the sidesurfaces 107 of stem portion 16 and a minor diameter N, of the order of0.015 inches, extending in the direction of the front and back surfacesof the stem. Discs 18 of this example are also slightly wedge-shaped invertical cross-section, having a greater thickness near a trailing edgeof the machine direction in which they are manufactured (FIG. 4A), asfurther discussed below.

Fastener product 10 can be formed by the method and apparatusillustrated in FIG. 12. Thermoplastic resin 31 from extruder 29 isintroduced into nip 32 formed between a supporting pressure roll 34 anda mold roll 36. Pressure in the nip causes thermoplastic resin 31 toenter blind-ended stem formation forming cavities 38 of mold roll 36while excess resin remains about the periphery of the mold roll and iseffectively calendared to form base sheet 12. As the rolls 34, 36 rotatein opposite directions (shown by arrows), the thermoplastic resinproceeds along the periphery of the mold roll until it is stripped fromboth the mold cavities and the roll periphery by stripper roll 40. Theresulting product has base 12 with integrally formed stem formations 104protruding therefrom as described above. The direction of travel of thematerial illustrated in FIG. 12 is referred to as the “machinedirection” (MD) of the material and defines the longitudinal directionof the resulting preform product 9 and fastener product 10 (indicated byarrows MD in the figures).

A more detailed description of the process for forming such structuresprotruding integrally from a base is described for instance in U.S. Pat.No. 4,775,310, issued Oct. 4, 1988, to Fischer, the entire contents ofwhich are hereby incorporated by reference. In preferred cases the moldroll comprises a face-to-face assemblage of circular plates or rings,some having cutouts in their periphery defining mold cavities and othersbeing circular, serving to close the open sides of the mold cavities andserve as spacers.

Once preform product 9 has been stripped from mold roll 36, it proceedsthrough guide rolls 42 to a head shaping station 50 where the loopengageable heads 18 are formed. Various techniques and apparatus forperforming the head shaping function of station 50 are now to bedescribed.

Preferably, as previously described, preform product 9 initially passesadjacent a non-contact heat source, e.g., the combustion products from agas flame 66 (indicated by dashed lines in FIG. 12), arranged to heatthe tips of stem formations 104. Subsequently, preform product 9 passesthrough predetermined gap 60 formed between rolls 62 and 64 and the tipsof stem formations 104 are contacted by a conformation roll 62, asdescribed above.

Gap 60 is less, by a controlled amount, than the overall thickness ofthe preform product 9 from the surface of the base opposite the stemformations to the tip of the protruding formations. Thus, the tipportions of the formations contact the roll and are compressed to causethe material to be flattened or formed in the area of 60, in apress-forming action which is sometimes referred to as “flat topping,”though final product may in fact not be flat due to desiredconformations applied to the head surface, as with conformation rolls8-8D, or as a result of further forming influences that follow thepress-forming action.

In the presently preferred form, roll 62 is cooled to temperaturessignificantly below melt or softening temperature of the resin,preferably to a temperature less than the ambient condensationtemperature of water for reasons mentioned. A surface temperature of 5°to 60° C. is operable over a wide range of products; for thesespecifically described here, it is preferable that the surfacetemperature range be between 10° and 45° C., surface temperature between25° to 30° produce excellent results in cases where the temperature ofthe combustion gas in which the formation extremities are immersed is inthe vicinity of 1000° C. or slightly higher.

In an alternative construction the head 18 is shaped by passing thepreform product 9 through a gap 60 formed between a heated roll 62 andan unheated or cooled support roll 64. A more detailed description ofthis type of “heated surface” head forming process is provided in U.S.Pat. No. 5,679,302 issued Oct. 21, 1997, to Miller et al., the entirecontents of which are hereby incorporated by reference. Even in the caseof using such hot roll forming as taught by Miller, it is recognized,according to the present invention, to be advantageous to employnon-contact preheating to forming temperature with especial advantagebeing obtained using the combustion gas convection heating as describedin which the side surfaces of distal portions of the formations areimmersed in the hot combustion gases to achieve rapid heat transfer byconvection and hence faster line speed and more economical operation.

In yet another example, which is also slow relative to the non-contactheating system of FIGS. 5, 6 and 12, an ultrasound roll is employed forheating and applying a desired head configuration. Speed of operation isenhanced by preheating with a non-contact heater, i.e. a radiant block,or exposure to convective heat transfer with gas at lower temperature.

In the preferred case, roll 62 is a rotary ultrasonic horn and supportroll 64 is a rotating anvil. In this example, more clearly illustratedin FIG. 13, anvil roll 64 is mounted on a reducer 65 that allows thevertical position of anvil roll 64 to be adjusted, thereby allowingadjustment of gap 60. A motor 68 drives anvil roll 64 to pull preformstem material 10 into gap 60. Meanwhile, a vibration is imparted torotary horn 62 causing its outer surface to oscillate at a frequencytypically between 18 and 60 kHz. Horn 62 is arranged to vibrate andcyclically compress the contacted portions of the stems as they passthrough gap 60, the vibration occurring at a frequency that causes thetips of thermoplastic stem formations 14 to flow and be formed by thecontacting surfaces. The result is a flattening deformation of the tipportions of the stems to form the disc-shape, loop engageable heads 18of FIGS. 11A-C. Subsequently, fastener product 10 is accumulated ontake-up rolls 69. More detailed descriptions of ultrasonic horn andanvil arrangements suitable for use in the above-described process aredisclosed in U.S. Pat. No. 5,087,320, issued Feb. 11, 1992, to Neuwirthet al., and U.S. Pat. No. 5,096,532, issued Mar. 17, 1992, to Neuwirth.The entire contents of both of these patents are hereby fullyincorporated by reference.

In the diagram of FIG. 13A, it is seen that the path of travel of thesurface of rotary horn 62 is in the machine direction, m.d., of thestem-forming machine. In this case, the horn surface may function as apressing or flat-topping surface to reform the top portion of thetraveling preform elements.

In the diagram of FIG. 13B, the rotary ultrasound horn 62 a has a planarcontact surface arranged to brush over the tops of preform elements,with components of the brushing motion extending in all quadrants,creating multidirectional hooks, including, importantly, hooksoverhanging their base in the cross-machine directions. An optionalwater spray may be introduced in advance of the stems to serve as acoupling agent to prevent adhesion of the stems to the vibratingsurface. By suitable choice of resin, melted resin at the tops of thestems, resulting from the vibration is brushed plane-wise into the formof thin disc-form heads at the ends of the stems.

In another embodiment, illustrated in FIG. 14, an alternate techniquefor producing preform stem product 9 is employed. The process is similarto that described above with reference to FIG. 12 except only a moldroll is used, i.e., no pressure roll is necessary. Here, the extruderhead 29 is shaped to conform to the periphery of the mold roll and theextruded resin 31 is introduced directly to a gap formed between themold roll and the extruder head. The remainder of the process proceedsas described above with reference to FIG. 12.

The shape of the engaging heads 18 of the fastener product is dictatedby a number of parameters. For example, the wedge shape illustratedparticularly in FIG. 11A is commonly the result of the dragging of thehead portion of stem formations 104 as they are deformed in head formingstation 50 of FIG. 12. Thus, the wedge is thicker at the rear edge ofthe engaging head as the material is pressed rearwardly while base 12moves forward in the machine direction. The difference in thicknessbetween the front and rear of the wedge can be adjusted by, e.g.,process speed, heat applied (if a heat deformation process is used) andby the adjustment of deforming gap 60.

It is found that particular forms of the shape of stem formations 104 ofpreform product 9 significantly affect the loop-engageability propertiesof the male fastener needed, and important aspects of the presentinvention concern these preform products per se, as well as theireffective use in the various forming systems described, and especiallysystems employing non-contact heating and/or melting. In one example,illustrated FIGS. 15A, B and 16A, B and C, a relatively short stemdesign is employed. The preform stem height, L_(h), is of the order of0.018 inches, a width, w, of the order of 0.008 inches, and a length, lof the order of 0.008 inches, again providing a stem of squarecross-section. While the engaging head 18 (FIGS. 16A-16C) formed fromsuch a preform element can have the same dimensions as the tallerfastener element previously described above with reference to FIGS.11A-11C, the shorter stem portions enable the fastener elements to bemore rigid.

In the embodiment of FIGS. 17A, B and C, a particular preform stem shapeis used to determine a final fastener product 10 having engagementcharacteristics different from the above described examples. Preformstem 120 has a first stem portion 122 attached to base 12 and a secondportion 124 that extends from portion 122 to define the overall heightof the formation. The stem portion 122 extends to a height, h₁, of theorder of 0.019 inches, the second portion 124 has a height, h₂, of theorder of 0.008 inches, the overall height, h₃, of the formation being ofthe order of 0.027 inches. Second portion 124 has outer wedges 117, 119at its front and back surfaces 121, 123 that are of triangular form withbase at the transition from stem portion 122 and peak or point at thetop or adjacent the respective surface 121, 123. Thus a “V” shapedcentral opening occurs that is devoid of thermoformable resin.

Referring now to FIGS. 17C and 17D, preform stem 120′ is a modifiedversion of the preform stem 120 described immediately above. Stem 120′has lateral extensions 125 of material that extend outward and upwardfrom wedges 117′, 119′. These lateral extensions, when reformed ordeformed, e.g., by flat-topping or any of the other stem reformingoperations disclosed herein, provide important features to the resultingfastener element. For example, lateral extensions 125 can be meltedand/or pressed downward to create or enhance base overhanging features,and these features can be particularly directed in the cross-machinedirection relative to the direction of stem manufacture. FIG. 17Dillustrates a series of mold roll plates 117″, 119″, 120″ that combine,along with outside spacer plates, to form a cavity capable of producingstem 120′ of FIG. 17C.

As illustrated in FIGS. 18A-18C, subsequent processing of stem formation120, using, e.g., one of the above described head forming techniques todeform substantially all of second portion 124 of the FIG. 17 preformelement can result in a fastener element 130 having a substantiallylarger major diameter, J, in the machine direction (MD) than its minordiameter, N, in the cross-machine direction. This asymmetrical headshape allows for a directional increase in peel and shear forces, as thelonger overhang in the machine direction retains, e.g., an engaged loopbetter than the shorter overhang in the cross-machine direction.

The opposite effect to that of the fastener element just described canbe obtained, for example, by using a preform stem shape such as thatillustrated in FIGS. 19A and 19B. Stem formation 200 has a first portion202 of height h₁ connected to base 12 and a second portion 204 of heighth₂ extending to define an overall height, h₃, of the stem formation. Thesecond portion 204 of the formation, beginning at a transition at thetop of first portion 202, tapers substantially on each side (e.g. at anangle greater than 20°) to provide a significantly reduced dimension wat the top. In an example, first portion 202 has a height, h₁, of theorder of 0.021 inches while the overall height, h₃, of the stemformation is of the order of 0.027 inches.

Deformation of substantially all of second portion 204, employing one ofthe above described techniques, to form an engaging head, results in thefastener element 210 illustrated in FIGS. 20A-20C. Fastener element 210has a major diameter, J, in the cross-machine direction substantiallygreater than its minor diameter, N, in the machine direction. The resultis a unidirectional increase in engagement forces due to the increasedoverhang of the engaging head in the cross-machine direction.

In another example, illustrated in FIGS. 21A and 21B, a stem formation300 has a first portion 302 of a first cylindrical shape and aconcentric second portion 304 of a substantially smaller cylindricalshape extends to define the overall height, h₃, of the formation.Deformation of substantially all of second portion 304, employing, e.g.,one of the above described techniques results in an advantageously thinengaging head, of thickness K₁, as illustrated by fastener element ofFIG. 22. This small thickness is a result of having substantially lessmaterial in the deformed head portion than in traditional preformedstems. Such thin engaging heads are advantageously capable ofpenetrating beneath loops with very little loft, a characteristicespecially exhibited by certain nonwoven materials, for instance, ultrathin nonwoven materials used e.g., in inexpensive packaging applicationsin which few cycles of opening and closing are required.

FIG. 23, a highly magnified perspective view, shows a novel quadrolobalhook created by heating and pressure-heading a quadrolobal stemcomprised of thin fins 21 extending along the X axis and thin fins 19extending along the Y axis, that have been heated and reformed at theirouter extremities to form hook head 18.

In the side-view of FIG. 23A, and plan view of FIG. 23B, dimension Mdenotes the head width in the X axis, N the width in the Y axis, K thehead thickness, L_(h) the overall hook height, L₁ the stem height priorto pressure-heading and S the overhang of the hook head beyond the sideof the stem. For example the dimensions may generally range as follows:

General Range Preferred Range M = 0.004 to 0.070 inch 0.010 to 0.020inch N = 0.004 to 0.070 inch 0.010 to 0.020 inch K = 0.002 to 0.015 inch0.002 to 0.005 inch Lh = 0.007 to 0.120 inch 0.025 to 0.045 inch L1 =0.010 to 0.160 inch 0.030 to 0.050 inch S = 0.001 to 0.015 inch 0.003 to0.005 inch

As shown in FIGS. 23C and 23E the stem is of a “plus sign” cross-sectionprofile, fins 21,19 extending symmetrically along the X and Y axes inboth directions from a common intersection. The fins have the samelength F, G, the same thickness B, H and the same height L₁ prior topressure-heading.

The fin profile ratio for the X axis fin is F/H and for the Y axis fin,G/B.

The concept of this hook preform element is that with a fin ratio ofgreater than about 2, preferably around 2½, an improved head overhang isobtainable at the end regions of the fins, see the series of FIGS.23F-A-23F-E for an illustration of the “balling effect of unorientedresin along the top edge of a thin fin, and note the bulbous overhangsat the thin ends of the fins.

With the stem preform of FIG. 23, such overhangs are provided in eachsense in orthogonal directions.

According to this aspect of the invention, a ratio of less than about 2is seen generally to result in a stem that, when heated andpressure-headed, a head of approximately the shape of a circle centeredon the center of the stem results. With a fin ratio of about 2,preferably between 2 and 4, most preferably between about 2½ and 3, thegeometry differs significantly from a square or circular cross-sectionstem such that when heated, surface tension of unoriented polymer willform lobes on the ends of the fins that remain somewhat independent, seeFIGS. 23F and 23F-A-23F-E, this being especially the case whennon-contact heating is employed, with immersion of the side surfaces inthe hot convection gases, down to the end of the dashed lines in FIGS.23A and 23F-E.

Whereas, in general, the extent of non-contact heating is preferablyfrom about 15 to 25% of the total length of the protruding formation, inthe special case of convective heating with gases that, from flamecombustion, can be about 1000° C., the percentage length heated extendsto 30% with good results obtainable.

The presently preferred method for forming this product is shown in FIG.23G, FIG. 23G′, 23G″ and FIG. 23H. Extruder 29 provides a travelingmolten resin strip to a roll stack comprised of rolls 1, 2, 3 and 4,numbering from bottom to top. The plastic passes through the nip betweenrolls 1 and 2. Roll 2 is a mold roll, its exposed outer surfacecomprised of mold cavities such that the molten polymer flowing into thecavities takes on the form of the cavity and then is de-molded toprovide preform stem 104 of substantially unoriented resin. It is one ofthe features of this invention that, by the use of non-contact heating,especial advantage is taken of the unoriented nature of the polymer toenable surface tension effects to act to strategically locate and sizethe deformable mass of polymer that highly desirable effects areobtainably by the “flat-topping” i.e. press-forming action.

Referring to reference to FIGS. 23G, G′ and H, an array of stemsintegral with a backing sheet 18, with extent in both X and Y directionsare thus molded by roll 2, and are demolded about a take-off roller 5 inmaking the transition to roll 3. On roll 3, close to the nip withconforming roll 4, the end portion of the stems pass under a non-contactheat source as a first step to create the hook heads 18.

In this embodiment, the non-contact heat source is a close-lying gasburner, and the sides as well as the ends of terminal tip portions ofthe stems are immersed in the hot gases produced by the burner. Thus thesides are rapidly heated by convective effects as are the top portions,which also receive radiative heating. Given the high surface areaexposed to the intense heat, compared to the bounded volume of resin ofthe exposed terminal portion of the structure, this portion is rapidlymelted, with highest temperature and lowest viscosity achieved at theprojecting ends of the profile of the thin fins. An example is shown inFIG. 23F.

As also shown in the diagrammatical blown-up view, FIG. 23H, surfacetension causes the molten plastic to form as a cylindrically roundedmass along the fin length ending in segments of spheres or balls at theends of the fins. The circular forms 105 of FIGS. 23G and H are symbolicof the molten form, the precise form depending upon the length tothickness ratio of the fin profile, as well as the selection of theresin and degree of heating, controllable parameters of the process.

In this condition, the stems pass between another nip created betweenrolls 3 and 4, in which roll 4 presses down upon the molten polymer tipsand forms a flattened head shape, to form heads 18 of shape dependingupon the characteristics of this roll.

Preferably, the forming roll 4 is cooled, to remain at a temperaturebelow the molten polymer temperature, preferably considerably lower.

With the surface of roll 4 cooled to temperature below the condensationtemperature of steam, and in the case of use of flame from a burner toheat the stems in close proximity to a cooled conformation roll 4, wateras a combustion product from the burning gas fuel condenses on the roll4 and is found to act as a release agent for promoting clean separationof the formed heads and the surface of the roll as the headed hooks exitfrom under the forming roll. In this case both the cool temperature ofthe conforming roll 4 and the moisture promote clean release of theheads 18 from the roll surface without sticking of the heads to theroll, where that is undesirable. Best advantage is obtained by locatingthe point of heating close to the roll. In preferred embodiments the tipof the burner is within one centimeter of roll 3 and within 2½centimeters of roll 4, adjustment of the separation of the burner fromroll 3 serving as a control for the amount of convective heatingobtained.

The air gas mixture of the gaseous fuel and air is introduced to theburner in substantially stoichiometric ratio for optimum combustion,such that substantially complete combustion occurs, producing byproductsessentially only of carbon dioxide and water.

The burner may have a ribbon opening extending across the width of theweb, or may comprise jet holes, the spacing between holes being closerthan the distance to the heads such that because of air entrainment asubstantially uniform turbulent stream of hot gas reaches the topportion of the stems to be melted.

In one preferred embodiment a ribbon burner is used, providing acontinuous line of flame. The burner temperature is between about 1000°and 1200° C., produced with a natural gas feed, the primary component ofwhich is methane (CH4)CH₄+20₂→CO₂+2H₂O

Complete combustion uses 9.5 moles air for each mole of CH₄, thus oxygenin the air gas mix is (2 moles O2/10.5 moles total) equal to 19.0% O₂.

The burner face is approximately 1″ wide. The web carrying the stempreform travels at speeds in the range of 20 to 200 ft/min (dependingupon the product desired and operating parameters), and so a stempreform element spends only a fraction of a second underneath theburner. In this amount of time a sufficient amount of heat istransferred into the preform element to enable it to be deformed into ahook. Heat is transferred to the preform element by forced convection.Heat is transferred through the stem tops as well as sides. The amountof heat transferred to the preform element, is controlled by theposition of the burner relative to the elements.

Simple steps may be followed in set-up for such flat-topping.

-   -   1. Extrude and form a web of preform stems on a continuous        backing, as described above.    -   2. Set gap position of the forming roll (Gap between rolls 3 and        4) at a position that corresponds with desired hook height while        stem forming is occurring. At this point stems passing through        the gap will buckle since their tips are not being heated.    -   3. Turn on the burner and, step-wise, bring the burner closer to        the terminal ends of the stems. The burner position will        typically vary from 0.2″ to 1″ from roll 4. The flame set-up        (i.e. flow conditions) is maintained constant, so that the only        variable altered is the position of the burner with respect to        roll 3.

In some cases the line speed is dependent upon the amount of heatdesired to be transferred to the stems. For instance, comparing 2 setsof stems, Group A: 0.008″×0.008″×0.027″ vs. Group B:0.012″×0.012″×0.075″. Group B requires more heat per stem, and passingheat through a larger body requires more time for heat to be transferredsuch that Group B may run at a speed ⅓ that of Group A.

The mold cavities in roll 2, FIG. 23G, are shown in FIGS. 23I-23M. Rings70 and 72 are placed face-to-face together in registry such that whenviewed from a plan view down upon the periphery of the mold ring pair, aplus sign mold shape is provided, with fin shaped cavities of betweenabout 2 and 3 length to thickness ratio in accordance with the providedexplanation. Many sets of rings are placed side-by-side and pressed ontoa shaft, providing an axial distribution of peripheral rows of cavities,FIG. 23N. The size of the cavities and their distribution is selectedaccording to the needs of the particular fastening system beingconstructed. Typically a slight draft angle, e.g. of 1° is employed toenable the molded fin to readily leave its mold. As shown in FIG. 23N,solid spacer rings 73 having no mold cavities are placed between pairsof rings 70, 72. A first set of rings 70, 72 is spaced by a spacer ringfrom the next set, and so on. In the mold pattern of FIG. 23N the moldcavities of adjacent pairs are aligned axially of the mold roll.

In FIG. 23O, a typical off-set pattern is shown for the tool rings.Adjacent pairs of rings are off-set by 50%, as one useful pattern forenabling engagement with loops.

According to the concept of this embodiment, the plus sign cross-sectionstems 104 with thin fins 19, 21 when pressure-formed by conformationroll 4 will provide polymer flow in directions of the four lobes off theends of the fins. For diaper applications, for instance, wherecross-machine directionality of the hook is often important due to theorientation of the machine direction of the fastener in the diaperforming process, this can achieve better engagement with the nonwovenloop component of a diaper than by hooks formed with a round or squareprofile cross-section design.

To explain why the thin-fin quadrolobal stem preform will provide bettercross-machine directionality, referring to FIGS. 23P and 23Q, a squarestem with a circular head is shown. In the side view of FIG. 23Q a loopis shown attached to the hook. The loop extends upwardly, perpendicularto the bottom surface of the hook overhang. The case where the loop isbeing pulled directly away from the base of the hook can be explained byvectors as in FIG. 23R. In this case the force F exerted on the loop isshown as the vector coming from the outer portion of the hook head downto underneath of the hook head to the mid point of the stem. This vectormay be explained to be the sum of a vector A that extends tangent to thecircle to the point where the loop exits from underneath the bottom ofthe hook head, heading away from the stem, and a third vector B drawn at90 degrees, extending from the end of vector A to the end of vector F,to create a right triangle formed by side vector A, side vector B andhypotenuse vector F. The angle Φ between vectors A and F enables vectorA to be written as vector F consine Φ.

For Φ between 0 to 90 degrees, as Φ increases, vector A decreases, hencethe loop becomes less likely to slide off the hook when pulled.

This case is compared with one lobe of head 18 of a thin-fin hook, asshown in FIG. 23S, a top view. The loop filament is at the end point ofthe stem and is being pulled directly up as shown in FIG. 23T.

In this case, by vector analysis shown in FIG. 23U, the angle Φ isgreater than the angle Φ for the circles Φ_(fin) is greater thanΦ_(circle). The reason for this is, according to the present concept,the tips and short ends of a thin fin stem are deformed more compared tothe long section of the fin due to greater exposed surface area to theheating conditions. The greatest overhang of the hook head then is atthe end of the fin. This causes a tangent to the overhanging rim to becloser to horizontal (in plan view) than the tangent line of a similarround head, and the beginning of the widest portion of the head to beclose to the end surface of the thin fin. In the case of a circular headon a stem, the widest portion of a circular head (its diameter) lies atthe center axis of the stem structure rather than off-set as is the casewith the thin fin.

The concept described here rests in part on the proposition that the fintip heats locally towards its profile ends because of a higher surfaceto mass ratio, related to surface exposed to the localized, non-contactradiant or convection heat that reaches the side margins of the stem.

Consider the top end of the quadrolobal fins with points A on the end ofone fin, B in the middle where the two fins join and C on the end of theopposite fin. When passed under a non-contact heat source points A and Care predicted to acquire more heat per unit volume of polymer and areeasier to deform compared to point B. During pressure forming by roll 4,more resin is pushed off (deformed) in areas A and C compared to themiddle, B, because more heat per unit volume has been transferred to thesynthetic resin at those points, A and B, and therefore that resinreaches a higher temperature, and consequent lower viscosity, and morereadily flows in response to forming pressure.

For a typical square stem that has a cross-section size of 0.008×0.008inch, the head has approximately two times the width of the stem. Thusthe area of the footprint of an individual hook is 0.008²×π, or 2×10⁻⁴inches², while the stem cross-section area is of 6.4×10⁻⁵ inches². Witha thin fin stem construction of the same area of ratio of 2 to 1,(length×base=2.04×10⁻⁵), the thickness is about 0.0056 inches and thelength about 0.0113 inches. For the same size footprint, comparing theangle Φ between a square stem and a thin fin stem, the angle Φ isconsiderably greater with the fin for the same footprint than for the Φof the circular head, or said another way, a thin fin hook of equal peelperformance to that of a circular head will have a smaller footprint onthe loop surface.

Footprint is important for applications such as diapers, because a smallfootprint allows for good penetration into a low loop mass, whereas alarger footprint tends more to push down on the loops and not allow thecrook or bottom part of the head of the hook to enter under the loopsthat are pushed down.

This analysis indicates, further, that one can make a thin fin hook witha footprint less than that of a round head that will penetrate loopbetter, and get more engagement, and it can still be such that the looptends less to slide off than with the round head.

The relationship so-far described shows the difference between a circleand a fin when the hook and loop are being separated in tension mode,i.e. at their stages of peel which are in tension mode, when the loop ispulled at an angle close to 90 degrees to the base of the hook.

The benefits of a fin may be further explained considering the conditionin which the hook is subjected simultaneously to a component of sheerloading. FIG. 23V shows a flat top hook in which the loop is beingpulled back at an angle between the loop filament and an imaginaryhorizontal line extending across the bottom of the hook head in the X, Zplane. When angle θ is introduced, with the previous vector work, anequation may be generated to show the relationship between θ and Φ, i.e.the relationship between the angle at which vector A is coming off theangle between vectors A and F. Vector A is the vector in which the loopis coming around the hook and angle θ is the angle relative to thebottom of the hook head. With angle θ=0 degrees, the loop and hook arein perfect sheer mode and with angle θ=90 degrees, the loop and hook arein perfect tension mode. This enables an equation to be generated, withthe vectors added, to show a minimum no-slip condition effect, angle θminimum in relation to Φ minimum is equal to the inverse cosine of thegroup of cosine Φ divided by sine Φ. From this relationship a graph iscreated, FIGS. 23X, that shows the minimum no-slip conditionrelationship between Φ and θ, angle Φ being the angle between vectors Fand A and vector A being the force tending to cause the loop to slideoff the hook. It shows that for an angle Φ of less than or equal to 45°,θ minimum must be 0. A loop will slide off unless it is in perfect sheermode for Φ equal to or less than 45 degrees. This graph also shows thatthere is a sharp portion of the line between Φ=45 and Φ=50 degrees. Itis realized that any small increase in Φ between angles from 45 to 50degrees results in a much larger difference in what is required for θminimum. Small improvements in Φ result in less of a necessity to be inperfect sheer mode.

An important aspect of the invention concerns the realization that smallchanges in the head configuration can give relatively larger benefits;hence the important advantage of the thin fin construction for peelmode. Explaining further referring to FIG. 23Y a hook component is shownbeing peeled from a loop component. At the bottom area of the valleybetween the hook and the loop component the forces are substantially intension mode, angle θ being close to 90 degrees, because no sheer forceis involved. The hook is being pulled directly away from the loop at thebottom of the V during peel mode, similar to the application of forcesshown in FIGS. 23P and 23T. Now, so long as the hook can hold onto theloop, as it moves up the V, angle θ starts to decrease.

If a hook at the horizontal portion of the fabric is still mated with aloop, all force is in the shear mode, i.e. resisted by the stem.

This shows the importance of having a large Φ angle to avoid dependenceon the θ angle. It is believed the fin designs will have a higher Φangle when compared with a standard round head product. Therefore, forany given θ angle, the fin design should be less likely to slip whencompared to a standard round top hook. These calculations were made withthe assumption of no friction; the loop conforms to head shape, thusloop stiffness is negligible, gravity is negligible and the hook is arigid body.

The analysis applies to a plane single fin, and to the fins 19, 21 of aplus-form hook as well, and to other configurations that provide flow orforming capabilities to increase angle Φ.

In condition where only cross-machine peel strength is important, a hookcomponent formed with single fins lying cross-wise can be employed.

The plus-form or the “quad” configuration allows one to engage indiffering directions.

FIG. 24 is a 3-D (three dimensional) view of the quadrolobal hookcreated with (see FIGS. 24C and 24D) fins 21′ in the X axis that areshorter than the fins 19′ in the Y axis to form a hook 10 with betterloop engageability in the cross-machine direction because the profilecauses more polymer in the cross-machine direction to be heated andsubject to forming a hook compared to the polymer of fins in the machinedirection.

In certain instances the fins 21′ may be so short that their outer tipportions are not reformed by roll 4. In such case, the X-direction finsact as supports for fins 19′.

FIG. 25 is a top view of a hook created with Y axis fins 21″ and 21″′offset from each other, neither being at the center of the X axisstructure.

In the case of FIG. 25 fins 19″ protrude at the extremities of the Xaxis structure beyond fins 21″, at the forming station at roll 4.

In the alternative embodiment of FIG. 25D the Y direction fins are atthe extreme ends of the X direction structure.

Likewise, of course, where the effect is desired for the machinedirection, the stem cross-section may be placed at 90° to that which isshown in FIG. 25D.

As shown in FIG. 25D this forms an irregular shaped hook. Under certainconditions, as shown, the head has bulbous ends and reduced widthsection in-between, e.g. a dog bone or bow tie configuration. Such aconfiguration enables a loop, that passes the widest point of the hook,to slide towards the middle of the hook, where the head is narrower,effectively trapping such loops to improve hook-to-loop engagement.

FIG. 26 is a side-view of a four feature hook created with X axis fins21A of considerable length, and Y axis protrusions 17 that are veryshort in machine direction md. The Y axis protrusions 17 serve tosupport the hook during formation and in use as well. Importantly theyreduce the foot print of the hook, allowing for easier penetration intothe loop mass e.g. of thin nonwoven fabrics.

FIG. 27 is a top-view of a quadrolobal hook formed with a conformationroll having an array of embossing features much smaller than the headdiameter, indicated in the form shown, as square projections.Penetration of these projections into the top surface of head 18 duringits formation, serves to displace resin to a useful degree, to theundersurface though not to as great a degree as at the top surface. Thisprovides roughness or rigidity to the undersurface and edges of thehead. Such features provide mechanical obstacles or “catches” to thesliding of loops along that surface, and hence enhance loop engagement.

In other embodiments, pointed pyramidal shapes, rounded dimples and theimprint of randomly placed particles such as those of sandpaper can havelike effect on the edges or undersurface of the head.

Preferably, at least three of such deformations are employed and, exceptin the case of relatively fine sandpaper, preferably there are less thanabout 15 of the deformations to avoid “wash-out” of the effect.

In certain cases the surface features of the conformation roll areselected to force resin from one X, Y location to another to enhancehead overhang in some regions, decrease it in others, or provide edgefriction points for improving loop engagement.

The hook form of FIGS. 28 and 28A has the head 28″ shifted to one sidealong axis A aligned with the machine direction. This form can becreated by over- or under-driving the forming roll 4 of FIG. 23G. Hooksof this type are useful in applications that require one-directionalengagement.

It is useful to explain use here of the term “superheating.” In general,the non-contact heating step described, when the gas flow rate andorifice sites are set has an established range of heating capabilitythat is controlled by the distance of adjustment and is independent ofthe particular polymer. Using the set-up technique described above, theheating is readily adjusted to enable flat-topping and stabilization ofthe forms shaped by the cold forming roll 4. By adjusting the distanceof the burner closer to roll 3, more heat than the minimum required forflat-topping can be applied. The system remains within the range of theflat-topping action. In that case, flat-topping is effective todistribute the resin and apply a shape, but a point is reached at whichit is readily observed that the emerging forms have not yet frozen, andfurther, predictable deformation is observed.

It is realized that benefit can be obtained from this secondary,“self-forming” action.

In one case, by choosing a resin having a low heat deflectiontemperature, the method is useful to form rounded mushrooms of theself-engaging fastener type. For the example of FIGS. 29-29A, lowdensity polyethylene (LDPE) having a heat deflection temperature of 113degrees F. was employed (significantly lower than the heat deflectiontemperatures of 186 degrees F. and 204 degrees F., of high densitypolyethylene (HDPE) and polypropylene (PP), respectively). (For nylonand High Density PE, see FIGS. 30, 31.)

With a given coolant flow through the cold forming roll 4, aftersatisfactory flat-topping of the LDPE heads was established with frozenshapes emerging, the heater was brought closer to roll 3, and the linespeed slowed to apply excess heat. As heating was increased, gradualchange in the final conformation of the flat-topped product wasobserved. A point was reached in which, in a stable process, the roundedmushroom shapes shown in FIGS. 29-29C were produced. In this caseflat-topping was effective to flatten and spread the bulbous moltenpolymer, and following roll 4, the mass sank and rounded to the formshown. Two components of this shape were effectively engaged to serve asa self-engaging fastener as depicted in FIG. 29D.

Thus, the embodiment of FIG. 29 is formed employing an initial preformstem of the form of that of FIG. 23C, however parameters are controlledto form a rounded upper profile. In addition or in combination withprevious techniques mentioned for forming round tips, it is found thatresin selection and an extra degree of melting, produced by“super-heating” at the non-contacting heating steps can be usefullyemployed.

By choice of low deflection temperature resin, e.g. certainpolyethylenes, and either by making the fin construction very thin andor subjecting the tip portion to large heat transfer by the proximity orintensity of the flame, a condition can be obtained in which usefulgravity flow of resin occurs after passing by roll 4. This condition canfor instance also be obtained by maintaining roll 4 at such temperaturethat it does no entirely solidify the tip portions.

With higher deflection temperature resins, e.g., high densitypolyethylene, a useful self-bending action of outer edges of theflat-topped structure form the “J” profile mentioned.

The process of forming the stem preform by filling dead-end mold voidswith polymer, does not orient the polymer. As previously mentioned,heating this preformed stem results in a ball of molten polymer at thetop of the stem. After heating, the molten top is reformed with a flator configured forming roll to form a head structure extending out in alldirections to an extent dependent upon the height and mass of thereformed portion.

In the pictures of FIGS. 29, 29A a low-density polyethylene resin waschosen. The tip portions were super heated, i.e. heated in excess ofthat to be removed by cold flat-topping to retain residual gravity flowcapability.

Following flat-topping, the flattened resin head gathers under surfacetension to form a well shaped mushroom head.

Under essentially the same thermal conditions, the flattened head ofnylon and high density polyethylene bent bodily to turn down theperipheral tips of the heads to provide a J profile, see FIGS. 30 and31.

FIG. 32 is a side view of a quadrolobal hook with a curved head that hasportions at the fin ends shaped as a J style hook. This is accomplishedby choice of the resin of which the preform stem element is molded andappropriate control of the non-contact heating and of the end of thestem and softness of the head following reformation by the conformationroll; e.g. roll 4, to enable a degree of slump of peripheral portions ofthe resin following flat-topping.

The amount of heat provided prior to the forming determines whether thepolymer will flow while, as shown by comparison of FIGS. 29, 29A withFIGS. 30 and 31, the type of resin determines the shape of the formedhead and down the stem giving a curved head or whether the ends of thehead bend down to provide the J style referred to. The resultant J formis beneficial to retain loops trapped underneath the head.

FIGS. 33, 33A and 33B, perspective, side and top views, respectively,show a quadrolobal “M” hook, so-named because of the configuration ofthe preformed stem from which it is formed, shown in correspondinglyFIGS. 33C, D and E and FIGS. 33G, H and I illustrate mold tooling forthe element of FIG. 33.

Referring first to FIGS. 17A and 17B, that preformed stem has morepolymer at the outer-most portions of the stem in the machine direction,the amount of polymer decreasing linearly moving toward the center ofthe stem V.

FIGS. 34C, D and E show a similar M stem preform element, oriented inthis case in the cross-machine direction, and conceptually formed of two“half M” configuration stem segments, see the corresponding mold toolingshown in FIGS. 34F through 34J.

In the cases of FIGS. 17A and 34, the principle of the thin fin isemployed, having more of the resin concentrated at the X direction endsof the fins, adjacent vertical surfaces of the formation. Depending uponthe method of deformation, an oval such as the machine direction oval ofFIG. 18 or the cross-machine “FIG. 8” head of FIG. 34B can be obtained.With the quadrolobal M stem of FIG. 33 similar deformations can beobtained. In the case of the hook depicted in FIG. 33, non-contactheating provides four lobes of molten resin, concentrated at theperiphery, see FIG. 33F. Flat-topping of this resin can then produce thehead 18B shown in FIG. 33B. The resin, as it melts, finds the path ofleast resistance to be predominately at the “precipice” provided at thesteep sides of the M, with the desirable result of forming a large Φangle in the flat-topped product, according to the analysis presentedearlier. If a “super heating “condition” is employed, with resins suchas Nylon and high density polyethylene, J-shaped profiles are obtainableat the corners.

The M-configuration can usefully be reformed to provide aloop-engageable head by contact heating techniques as well, thoughpotentially at slower speeds. Thus the hot roll and ultrasoundtechniques described above with respect to FIGS. 12 and 13 may beemployed to obtain head shapes that may, in the case of ultrasound orlow level heat forming by a heated roll, be more sharply defined assuggested by FIGS. 34 and 34A.

In the case of the non-contact melting followed by flat-topping, stepscan be taken also to limit resin flow back toward the center of the “V”shaped void, as suggested by FIGS. 34 and 34A, for instance by limitingthe non-contact heating so that only the sharp tips of the M arerendered molten, while the larger cross-sections further down thewedge-form section are rendered mechanically deformable but not molten.Following this, flat topping with a chilled roll below the softeningtemperature or in some cases with a heated roll at or even above thesoftening temperature, provides useful hooks for some applications.

FIG. 34A′ depicts the profile of a hook provided by the flame heat-coldroll technique, the thicker hook tips being attributable to thenon-contacted heated resin that melted and rounded under surface tensionprior to the flat topping action.

FIG. 33, the 3-D view of a quadrolobal M hook has larger outer marginportions of the hook head overhanging compared with the hook of FIG. 23.More polymer on the outer portion of the fin is created from a stem thathas more polymer on the outer portion of the fins and the distributionof polymer and its proximity to the heat source decreases towards thecenter of the stem as shown in FIG. 33C.

According to this aspect of the invention, the more the hook headsextend past the stem is beneficial for forming a crook for betterengagement, to obtain better holding of loops underneath the hook. Agreater distance is then required for the loop to slide off when it isat the top of the stem. When it is at the end of the stem underneath ofthe head, a greater distance is required for the loop to travel aroundthe head of the stem before disengagement hence the loop will be heldbetter.

FIG. 34B is a top view of FIG. 34A that shows the head of the hook isformed in the cross-machine direction, showing that the bulk of thepolymer has indeed been pushed out to the side.

In FIGS. 34A and 34B the Φ angle is approaching 90 degrees, in thiscase, being high because of the large amount of polymer pressed out tothe side. At the loop along the base underneath the hook, by the stem,is at approximately the widest portion of the hook. Therefore, the Φangle will be very close to 90 degrees and the tendency of the loop toslide off will be very low.

FIG. 34A′ illustrates a hook profile similar to that of FIG. 34A.

In FIG. 34G the tool ring shown is cut at a 30 degree angle, so thatwhen one of the rings of these figures is flipped over and two areplaced together, they provide the center two rings of the mold of FIG.34F. The rings form a peak together, FIG. 34G. In FIG. 34F two outerspacer rings make-up the beginning and end portion of the M profile.

In FIG. 34F, the four different rings are 40, 42, 44 and 46, ring 42being the one turned over 180 degrees and otherwise is the same as ring44.

FIG. 35 shows another alternative of the M style hook in which a smallrectangular block is placed between the two halves of the M. This designprovides a bigger cross-directional hook. Referring to FIG. 35A itallows more volume of polymer to be excluded between the two hooks. Whenthis preform formation is flat topped, even more resin is pushed out tothe sides. FIG. 35A′ illustrates a hook profile similar to FIG. 35A butformed in a different manner.

FIG. 36 comprises one side of the M hook design sometimes referred to asan “N” design. It can be used by having half the rings face to the leftcross-machine direction and half the rings face to the rightcross-machine direction. It enables heating and flat topping a stem tomake a hook that bends in one direction in the cross-direction. Thebenefits of this hook compared to the M hook are a smaller footprint andallowing better penetration into the loop mass, yet still havingcross-machine direction features. FIG. 36A′ is a hook profile similar toFIG. 36A but formed in a different manner.

FIGS. 37-37B show a hook element again formed entirely by actions in themachine direction to have significant peel properties in thecross-machine direction.

In this embodiment a monolithic fin has a parallelogram profile incross-section as shown in FIG. 37E, with its long sides set at an angleof 45° to the machine direction and its short end surfaces aligned withthe machine direction.

As a consequence the pair of smaller opposed included angles at thecorners of the stem are only 45°, creating a localized region of the tipof the stem having a very high ratio of exposed surface to mass. Whenexposed to non-contact heating, and in particular to the hot gases of aclosely held flame heater, those corners preferentially melt, to bereadily deformed by the flat topping action, and indeed, when desired,can be super-heated such that desirable “J” formations can be formed asa consequence of the flow mentioned in respect of FIGS. 30 and 31. Suchhook formations have a significant component of orientation in thecross-machine direction.

On the other hand, the other set of corners with large included anglelocate a large mass of resin at the cross-machine extremity available tobe flattened into a strong loop-engaging disc structure havingsubstantial over-hang beyond the upright stem surface, leading to alarge angle Φ. Thus both corners of the parallelogram can contributesignificantly but differently to the loop-engaging function.

Referring to FIGS. 37F and G, the mold ring MR for forming the stempreform of FIG. 37C is formed simply by forming an angular passage fullythrough the thickness of the metal plate that forms the mold ring, thepassage having the required transverse profile end, the thickness of themold plate thus determining the thickness for the narrow dimension ofthe thin fin.

The alternating male fastener pattern of FIG. 37H is achieved byorienting the parallelograms of adjacent rows of molds in oppositeorientations. This is done simply by reversing adjacent mold tool rings,with a solid spacer ring SR face-to-face between each adjacent mold toolring pair. The bands of the fastener component in FIG. 37H thatcorrespond with the mold rings are indicated by I and I_(R) and thebands that correspond to the mold spacer ring are indicated by II. (“I”denoting one direction orientation of a mold ring and “I_(R)” thereverse orientation.)

Whereas one embodiment of the parallelogram construction may havestraight-sided stems as suggested in FIGS. 37-37E, another advantageousconstruction, especially for relatively tall fins, for providingcolumnar strength, has a thickened pedestal portion of the profile. Thisis readily understood from the mold cavity shown in FIG. 37G, of lengthL₁, with shoulder, of length L_(P), shown on both of the long sides.

This form is simple to manufacture. The parallelogram seen in the planview of FIG. 37F relates to the fin structure and its mold cavity asfollows. Parallelograms 430 and 438 correspond to the filet-definingstress-relieving transition at the base. The next inward parallelograms432, 436 represent the strengthening shoulders of the base pedestal ofthe thin fin, and the central parallelogram 434 represents the mainheight of the thin fin, extending to its tip.

All of these cavity portions appearing as parallelograms in FIG. 37Fextend at 45 degrees to the machine direction of the mold ring.

In a preferred embodiment, with total height L₁ of 0.05 inch, thepedestal height B may be 0.020 inch, to provide added columnar strengthfor the flat-topping operation, and, as well, to enable the mold toprovide clearance for removal of the entire fin structure from therotating mold by the usual expedient of turning about the stripping roll5. The mold ring plate thickness T, may for instance be 0.010 inchresulting in a diagonal tip to tip length for the fin of 0.020 inch, alength along each side of 0.014 inch a thickness t measured normal tothe long sides of 0.005 inch and an end profile thickness t_(p) of 0.007inch.

Taking the length of the fin as the full length of one side of 0.014inch and thickness t measured normal to that side of 0.005, the lengthto thickness ratio of this fin is 2.8.

With respect to the pointed ends of the fin, flat-topping of thoseregions can lead to a relatively small radius arc of considerable arcextent, with a resultant Φ angle approaching 90°.

It is anticipated when a loop is engaged on that point, the loop will beprone to pass down the sides away from the tip since it will not beriding along a directly opposed stem, but rather a stem that slants atan angle away from the end of the hook.

A sense of the loop engagement capability of the embodiments of FIGS.37-37G is obtained from the diagrammatic perspective views of FIGS. 37Iand J, taken from different points of view.

Another benefit of that hook is similar to that of the quadrolobal thinfin hook of FIG. 23, in that a footprint of size equal to that ofcurrent hooks manufactured, results in a larger Φ angle about the entirenarrow end of the fin. If a loop is engaged on that end it is believedthat the Φ angle will be larger compared to standard flat top productsthat have a square stem.

As has been indicated, the benefits of using convection heating from agas flame and forming with a cold roll are considerable.

The process allows the polymer to become molten and permits geometricconfigurations of the remaining formation and the flat topping step todetermine the direction of the polymer flow.

The cold roll is beneficial in that it freezes the polymer quickly. Thisenables high line speeds and relatively inexpensive production of hooksfor high volume applications.

Another non-contact heating approach is the use of a radiant heatingblock the heat from the metal, through radiation, with convection, heatsthe tips of the stems.

As has been mentioned, another way for forming similar hooks is theultrasonic method whereby vibration is used for localized heating anddeformation as determined by surfaces of the ultrasonic horn or theanvil.

A possible benefit is to obtain desired head shapes, as a consequence ofa more localized heating, avoiding effects of surface tension and hencenot requiring as large a fin ratio. It may also be beneficial inproviding more curvature of the heads and in making a head with asmaller thickness for improved loop penetration, but with the drawbackof lower line speed.

Another method used is a hot-wire method which would be a contactmethod. It would be with a heated wire. When the stems pass and touchthe wire they could then be formed by a forming roll or nip. Those wouldbe the main flat-topping methods.

Other features and advantages will become apparent from the followingDescription of the Preferred Embodiments, the drawings and the claims.

Another aspect of the invention is a composite fabric, and the making ofsuch fabric, on which stems have been directly molded in accordance, forinstance, with the teachings of U.S. patent application Ser. No.09/808,395 filed Mar. 14, 2001, which has been incorporated herein byreference above, followed by use of a flame of burning gas jets or thecombustion products flowing from the flame, to rapidly soften theextreme ends of the stems, followed by engagement by a cooled presssurface such as a cooled forming bar or a forming roll, as describedtherein. The numerous features of stem design and conditions of formingthe male fastener member as presented here are applicable to themanufacture of such composite materials.

A number of embodiments of the invention have been described.Nevertheless, it will be understood that various modifications may bemade without departing from the spirit and scope of the invention.Accordingly, other embodiments are within the scope of the followingclaims.

1. A method of forming a loop-engaging touch fastener product, themethod comprising: providing a preform product formed of thermoformablematerial and having a sheet-form base and an array of preform stemsintegrally molded with and extending from the sheet-form base, each ofthe stems including a first portion joined to the base and a secondportion extending from the first portion to a terminal end, anintersection of the first and second portions defining a discretereduction in transverse cross-sectional area of the stem, measuredparallel to the sheet-form base, from the first portion to the secondportion, an exposed top surface of the first portion defining ashoulder; and deforming at least some of the second portions toward theshoulder to form engaging heads configured to releasably engage a matingloop product.
 2. The method of claim 1, wherein the discrete reductionin transverse cross-sectional area occurs at a distance from a topsurface of the sheet-form base of at least halfway to the terminal endof the stem.
 3. The method of claim 1, wherein a cross-sectional areataken parallel to the sheet-form base near the terminal end of thesecond portion is less than 50% of any cross-sectional area of the firstportion, also taken parallel to the sheet-form base.
 4. The method ofclaim 3, wherein the cross-sectional area taken near the terminal end ofthe second portion is less than 25% of any cross-sectional area of thefirst portion.
 5. The method of claim 1, wherein each second portionprojects above each first portion without overhanging the sheet-formbase.
 6. The method of claim 1, wherein each first portion issubstantially rectangular in shape in transverse cross-section.
 7. Themethod of claim 1, wherein each second portion is substantiallyrectangular in shape in transverse cross-section.
 8. The method of claim1, wherein each second portion is substantially circular in shape intransverse cross-section.
 9. The method of claim 1, wherein each firstportion is substantially cruciform in shape in transverse cross-section.10. The method of claim 1, wherein each second portion defines a pyramidshape, the intersection of the first and second portions defining a baseof the pyramid.
 11. The method of claim 1, wherein each of the first andsecond portions have differently shaped transverse cross-sections. 12.The method of claim 1, wherein each first portion is cruciform in shapein transverse cross-section and each second portion is rectangular inshape in transverse cross-section.
 13. The method of claim 1, whereinthe deforming step includes heating the terminal ends of the secondportions with a non-contact heat source.
 14. The method of claim 1,wherein the deforming step includes heating the terminal ends of thesecond portions with a non-contact heat source, and then contacting theterminal ends with a contact surface.
 15. The method of claim 14,wherein the contact surface is maintained at a temperature less thanroom temperature.
 16. The method of claim 13, wherein the non-contactheat source is positioned about 0.1 mm to about 30 mm from the terminalends of the second portions.
 17. The method of claim 13, wherein thenon-contact heat source is a flame heater.
 18. The method of claim 13,wherein the non-contact heat source is a radiant heat source.
 19. Themethod of claim 1, wherein the deforming step includes heating theterminal end of the second portions by contacting the terminal ends withan ultrasonic horn.
 20. The method of claim 1, wherein each head has anoverhang aspect ratio, defined as an overall length of a chord extendingfully across the head, in top view in a machine direction, directlyabove a nominal lateral-most extent of the stem, divided by a maximumlateral extent of the head in a cross-machine direction beyond the stem,of less than 4.0.
 21. The method of claim 20, wherein the overhangaspect ratio is less than 2.5.
 22. The method of claim 21, wherein theoverhang aspect ratio is less than 2.0.
 23. The method of claim 20,wherein each head has a vertical head thickness, measured perpendicularto the sheet-form base from the top surface of the head to a lowersurface of the head, of not more than about 0.015 inch.